Just filled up the tank with 91 octane premium fuel

[darkmoon87]

Just to feel if there is any difference. (out of curiousity)

I didnt notice any power gain or anything like that, but one thing was quite noticable.


After installing my NST crank and waterpump pullies, the car became more sensitive to clutch and I had a little difficulty starting smoothly from 1st gear.
The car would shake more when I give the gas only as much as I used to give prior to the pulley install, so I had to be extra conscious with my clutch manuvering.

After filling the car up with 91, I can start from 1st gear with a relative ease. It starts noticably more smoothly.

Do u think this is just a placebo thing? Discuss.

[Aothachos]

Only time i used any gas under 91 octane is the day i got the car they filled it up with regular gas, after that day i filled my tank up with 91 octane ALL THE TIME NO MATTER WAT. It only costs like 20$ exact to fill up and lasts about a week the way i drive. My starts are usually instant no delay or anything, feels smoother ride for me, and i have an automatic but when i take off it feels so good like idk its weird but good

alot of ppl use 87 cause its a 'waste" of money to use 91 but idc im happy with my yaris on 91 hehe

[DerFlosser]

Possibly placebo but a higher octane fuel should ignite better so a smoother start really is possible.

[Thirty-Nine]

This is one of the long-standing debates on just about every automotive forum for cars that require at least regular unleaded gas.

Personally, I don't think there's any advantage to running anything higher than 87 in my Yaris. I've never noticed a difference in power or smoothness; just more cash at the pump. There are a ton of articles on the Internet about this, too.

Here's what the Federal Trade Commission thinks:

http://www.ftc.gov/bcp/edu/pubs/consumer/autos/aut12.shtm

Personally, I think if you think you're feeling a difference, it's a placebo.

[07WYarisRS]

Possibly placebo but a higher octane fuel should ignite better so a smoother start really is possible.

Higher octane fuel had a higher flash point... That means its harder for higer octane to ignite thats why its only to be used in high compression engines to eliminate knock...

So many people know so little about fuels and its affects its enough to make your head spin. Why people will continue to argue the effects of running different octanes is beyond me...
Run only the octane needed to prevent detonation, anything higher is waisting $$$ and costing you performance as a higher octane with higher flash point is harder to ignite and can waist fuel...
If your engine is knocking on 87 octane it either because you have a problem, your buyin shitty ass gas or you ran high octane fuels for a time and have a carbon build up problem.
i've been building and rebuilding race engines and regular engines for many years and have done many tests on the dyno and using CHT/EGT guages.
Facts are facts people. running a higher octane in a n engine that was designed to run a lower octane is not doing ANY good.. in fact it does more harm then good

[06vitzRS]

Higher octane fuel had a higher flash point... That means its harder for higer octane to ignite thats why its only to be used in high compression engines to eliminate knock...

So many people know so little about fuels and its affects its enough to make your head spin. Why people will continue to argue the effects of running different octanes is beyond me...
Run only the octane needed to prevent detonation, anything higher is waisting $$$ and costing you performance as a higher octane with higher flash point is harder to ignite and can waist fuel...
If your engine is knocking on 87 octane it either because you have a problem, your buyin shitty ass gas or you ran high octane fuels for a time and have a carbon build up problem.
i've been building and rebuilding race engines and regular engines for many years and have done many tests on the dyno and using CHT/EGT guages.
Facts are facts people. running a higher octane in a n engine that was designed to run a lower octane is not doing ANY good.. in fact it does more harm then good


+1

But i'm just a mechanic so what do i know.

It would be soooooo nice to put this topic to rest....probably not going to happen, oh well.

[eric81]

The book actually says to use 89 or better. Also, the better the octane, the better it will ignite on a more regular basis. I let my car warm up before driving it, and I find it helps all my components run smoother.

[yaris-me]

I don't thinks it's placebo effect. You may not gain power, but the engine timing can run a little more advanced. That can make it a little smoother. You can confirm this by switching back to 87 octane.:smile:

[jambo101]

On a recent trip from Tampa to Montreal i tried a tankful of the high octane just to see how/if it would show any difference on my Scangauge.Roads were through Georgia and the Carolinas so they were fairly consistant and cruise was set at 60mph
Average mpg on regular was 47.3mpg
Average mpg on high octane 47.3mpg
In fact all operating parameters according to Scangauge remained the same:iono:

[ddongbap]

Oh, I usually put that green handled gas in my car. Runs really weird though.

[Sabretooth]

Higher octane fuels are designed for high performance or just high compression engines.

You will feel a difference on a High HP engine, or even a Turbo application that is tuned specifically for 91/93+ octane fuels. I read somewhere that the Yaris is pretuned in the ECU to handle fuels with crappy octane levels (>87 Octane). So if anything 87 is enough.

[scape]

The book actually says to use 89 or better. Also, the better the octane, the better it will ignite on a more regular basis. I let my car warm up before driving it, and I find it helps all my components run smoother.

in the manual it states not to do this, especially during break-in, and recommend to simply turn it on and drive away.

as for octane, unless 89 is knocking, 89 is what your are to use. and 89 would only knock if it's lower than 89 octane, which can happen at very cheap gas stations.

"Higher octane fuels are designed for high performance or just high compression engines."
+1

[MUSKOKA800]

Do u think this is just a placebo thing?


Exactly,
Higher octane fuel burns slower to prohibit pre-ignition in high compression engines. Using higher than manufacturers minimum specification only subsidizes BIG GAS.

[scape]

Oh, I usually put that green handled gas in my car. Runs really weird though.

lol

[nerp]

The manual says to put in 89? Wha? Is that the Canadian 89?

[scape]

Canada might use RON, which is 91 equivalent to 87 Octane-- they also recommend use of fuel detergents to reduce buildup.

[DerFlosser]

higher octane fuel is a cleaner ignition assuming you have a healthy ignition system (all components). Other than than...one would really be hard pressed to tell the difference between an 89 and a 91 in a Yaris. It's a low-mid compression motor with 100hp. I can possibly see smoother starts but as far as running and gas mileage....we all know that the higher octane provides no benefits.

[ham]

Just to feel if there is any difference. (out of curiousity)

I didnt notice any power gain or anything like that, but one thing was quite noticable.


After installing my NST crank and waterpump pullies, the car became more sensitive to clutch and I had a little difficulty starting smoothly from 1st gear.
The car would shake more when I give the gas only as much as I used to give prior to the pulley install, so I had to be extra conscious with my clutch manuvering.

After filling the car up with 91, I can start from 1st gear with a relative ease. It starts noticably more smoothly.

Do u think this is just a placebo thing? Discuss.

I experience a noticeable gain in MPGs from 87 to 93

[Aothachos]

My manual says use 87 octane then in parenthesis next to it it says (research 91 octane) what does that mean? But yea no matter what no one is convincing me to go lower than 91 lol been using it my whole yaris life and no problems at all

[427chev]

The book actually says to use 89 or better. Also, the better the octane, the better it will ignite on a more regular basis. I let my car warm up before driving it, and I find it helps all my components run smoother.


Show me where "the book" says that.

Gasoline octane in the US is measured by the R+M/2 method, known as the PON number.

You're referring to the RON (reserach) octane rating, which is still used in Europe.

There is absolutely, positively NO ADVANTAGE in using a gasoline with an PON number greater than 87 on a Yaris. It is a waste of money.

[427chev]

I experience a noticeable gain in MPGs from 87 to 93


No you don't...

You might think you do, but objectively speaking there is no difference at all.

[BLAZINBLUEVITZ]

:thumbup: different thread SAME opinions.......

[The little red pill]

I just like the fact that running 91 octane gives me that 50 extra horse power. In fact, I raced a Mustang the other day and blew it's doors off! At the next light he asked me how I beat him. My response, "91 Octane Baby"!

P.S. I also have a AEM sticker on my car which throws in another 5 horsepower, but that's just our little secret! :cool:

[TheSilkySmooth]

if you have a CAI and open exhaust the ECU might retune over time for the higher octane and you might get some more torque, but I never found the need to add more than 2 gals to the rest of the tank in a mix to get all the octane the engine needs. try mixing in just 2 gals of 93 at a fill up of 87. Our engines are High compression and the eCU can start to retard timing when you get carbon buildup over time. A littel more octane can help. MAy car is starting to ping/knock at starting off in 1st gear at 20K miles on the odo. You dont drive hard enough to clean out this carbon, unless you run the car at WOT 3rd and 4th gear on the highway more than a couple minutes a day. That can clean it out. An melt your 2 layer exhaust pipe too!

[07WYarisRS]

higher octane fuel is a cleaner ignition assuming you have a healthy ignition system (all components). Other than than...one would really be hard pressed to tell the difference between an 89 and a 91 in a Yaris. It's a low-mid compression motor with 100hp. I can possibly see smoother starts but as far as running and gas mileage....we all know that the higher octane provides no benefits.

Higher octane does NOT have a cleaner ignition
Unless the compression is high enough to take ad vantage of the fuels flash point, burn rates and flame front speeds the engine will not burn as efficiently a a low octane and you end up with carbon deposits.
Lower octane fuels burn cleaner and more efficiently in ANY lower compression engines.
but I just build performance engines for a living and actually test them using the proper equipment..WTF would I know about fuels and the affects right?

Don't confuse RON and PON people
A 89 RON octane rating is PON (pump octane rating) of 86
when you look in the manual and see a research octane rating of 91 that does not mean to use 91 pumop octane... 91 RON = 87 PON.
Toyota, Honda and most other companies build thier econo engine to run on RON 89 (pump octane 86) because thats whats all thats available in some counties for low octane and it makes these engines most cost effective...

I'll never understand people that buy one of the cheapest econo boxes on the market and then run it on high octane ... you guys are nuts lol
you guys much know more then the dudes in white lab coats at toyota

[07WYarisRS]

if you have a CAI and open exhaust the ECU might retune over time for the higher octane and you might get some more torque, but I never found the need to add more than 2 gals to the rest of the tank in a mix to get all the octane the engine needs. try mixing in just 2 gals of 93 at a fill up of 87. Our engines are High compression and the eCU can start to retard timing when you get carbon buildup over time. A littel more octane can help. MAy car is starting to ping/knock at starting off in 1st gear at 20K miles on the odo. You dont drive hard enough to clean out this carbon, unless you run the car at WOT 3rd and 4th gear on the highway more than a couple minutes a day. That can clean it out. An melt your 2 layer exhaust pipe too!

our engines are NOT high compression... my street bikes run 200psi plug per cylinder and run on 87 octane... guess what they have less then 10:1 compression ration.

The ECU will not re-tune for higher octane...
The only time it will make a difference is if the engine is knocking... then the knock sesor will pick up the engine knock and retard the timing.. it won't change the fuel maps to compensate.

Spark knock AKA PING is completely normal and just means the engine is running efficiently...

running a lower octane fuel will reduce carbon built up as it has a lower flash point and will burn more efficiently and completely... Also start running a TRUE synthetic like Amsoil or Redline with no mineral oil or by products that cause deposits to form and after 10 years you engine will still be 95% carbon free

[highwaypass]

I experience a noticeable gain in MPGs from 87 to 93

i agree with you

[jambo101]

I experience a noticeable gain in MPGs from 87 to 93 Guess your car is different than mine as i see no difference Either through electronic measure or pencil and paper calculation but i guess if you are seeing noticeable gas mpg by paying the extra $$$ for higher octane then go for it , you will be happy with the extra mpg and the gas companies will be happy with the extra $$$$ Win win all around.

[Aothachos]

I experience a noticeable gain in MPGs from 87 to 93

+2 lol :thumbsup: i used to get 60 miles before the first bar went, now i use 91 it goes up to 75-80 on the first bar =), i wasn't satisfied with 60 miles on the first bar

also i had about half a tank of 91and i filled up with 87 and my car ran like crap like i felt it, it was horrible hard to explain but you feel it, like the car is "wtf is this crap your putting in me"



P.S. do you mean 91 or 93 lol

[BLAZINBLUEVITZ]

^^ the naysayers will NEVER believe you.....

[supmet]

I run 91 every once in a while, and it does feel smoother starting, accelerating, and idling.

Could it be a placebo affect? Maybe
Is it only a 2 dollar placebo, if it is? Yes


With the octane specific argument aside, aren't their cleaners and additives in 91 that aren't found in 87 at some gas stations??

[427chev]

I run 91 every once in a while, and it does feel smoother starting, accelerating, and idling.

Could it be a placebo affect? Maybe
Is it only a 2 dollar placebo, if it is? Yes

Not only could it be, it is.:rolleyes:

"CAR AND DRIVER" ran an article on this that included some objective testing of several vehicles. There was absolutely NO difference between regular and premium gasoline in vehicles that recommended regular (e.g. 87 octane).

There was a difference in vehicles that recommended premium, since running regular in them retards the spark and changes the engine mapping to the lower octane map.

[427chev]

+2 lol :thumbsup: i used to get 60 miles before the first bar went, now i use 91 it goes up to 75-80 on the first bar =)

So you're saying that running 91 octane in lieu of 87 octane increases fuel economy by about 30%..

Wouldn't Toyota simply recommend premium if that were the case? Premium only costs roughly 10% more, yet according to you it improves fuel economy by 30%. That means that running premium is a FAR more economical choice than running regular.

Honestly, anyone can claim anything on these forums. The fact of the matter is that I hold a mechanical engineering degree, have been employed in the profession for 23 years and have read quite a bit about the combustion process and fuel.

Scientifically speaking, your claim is baseless.

[BLAZINBLUEVITZ]

Honestly, anyone can claim anything on these forums.

and this is your claim:

I hold a mechanical engineering degree, have been employed in the profession for 23 years and have read quite a bit about the combustion process and fuel.
.
:laugh: :bs:

[427chev]

:laugh: :bs:

I've aleady won my argument with you, based solely on that fact that you resorted to (baseless) insults in lieu of a credible response that included objective evidence to back your "opinion."

Time and time again, objective evidence proves my point. In fact, the article below noted that the car designed to run on 87 octane actually ran WORSE on premium. That is not the first time I've seen that happen. I suspect that premium's slightly slower burn time might result in compromised combustion in some engines that are designed for regular fuel.

http://www.caranddriver.com/reviews/hot_lists/high_performance/features_classic_cars/regular_or_premium_feature/(page)/1

http://www.consumerreports.org/cro/cars/tires-auto-parts/car-maintenance/get-the-most-mileage-for-your-fuel-dollars-406/

"Don't use premium fuel if you don't have to. If your car specifies regular fuel, don't buy premium under the mistaken belief that your engine will run better. The only difference you'll see is about 20 cents more per gallon. Most cars are designed to run just fine on regular gasoline. Even many cars for which premium is recommended will run well on regular. We have found that the differences are imperceptible during normal driving. Check your owner's manual to find out if your engine really requires premium or if you can run on other grades."

[BLAZINBLUEVITZ]

I've aleady won my argument with you, based solely on that fact that you resorted to (baseless) insults in lieu of a credible response that included objective evidence to back your "opinion."



NO, your just a latecomer who thinks their gonna teach someone something with their knowledge. Maybe if this wasn't the 56th thread of the same topic id be a bit more receptive......

[427chev]

NO, your just a latecomer who thinks their gonna teach someone something with their knowledge. Maybe if this wasn't the 56th thread of the same topic id be a bit more receptive......

I have nothing to "Teach" anyone on this board.

Rather, I prefer to ignore children who have no understanding of the related science and will therefore remove myself from this thread.

[DerFlosser]

Higher octane does NOT have a cleaner ignition
Unless the compression is high enough to take ad vantage of the fuels flash point, burn rates and flame front speeds the engine will not burn as efficiently a a low octane and you end up with carbon deposits.
Lower octane fuels burn cleaner and more efficiently in ANY lower compression engines.
but I just build performance engines for a living and actually test them using the proper equipment..WTF would I know about fuels and the affects right?

Don't confuse RON and PON people
A 89 RON octane rating is PON (pump octane rating) of 86
when you look in the manual and see a research octane rating of 91 that does not mean to use 91 pumop octane... 91 RON = 87 PON.
Toyota, Honda and most other companies build thier econo engine to run on RON 89 (pump octane 86) because thats whats all thats available in some counties for low octane and it makes these engines most cost effective...

I'll never understand people that buy one of the cheapest econo boxes on the market and then run it on high octane ... you guys are nuts lol
you guys much know more then the dudes in white lab coats at toyota


I am not disagreeing with what you are saying. My point is that it's possible for the car to start smoother due to the higher octane fuel because, even though you may build engines and see drastically higher compression motors, 10.5:1 is still a "high enough" compression ratio to see benefits at start and idle condition utilizing a better grade fuel. I am not saying to run the car with the higher octane fuel...I am merely saying that it is a good possibility that the feeling is real in regards to the smoother start.

[Aothachos]

DAMMIT DARKMOON87 look wat you started lol, this is going to be the hot topic of arguments, like i said I know what i feel with 91 octane and I'm not changing, i don't mind putting in extra couple dollars for better fuel =)

*better fuel* watch someone say something about that lol

but yea im not convinced to switch to 87 so =) LET THE DEBATE CONTINUE!

[nerp]

All octanes have detergent in them. It's a bit of a misnomer to say that using 93 octane will "clean out" an engine that normally requires 87.

[07WYarisRS]

I am not disagreeing with what you are saying. My point is that it's possible for the car to start smoother due to the higher octane fuel because, even though you may build engines and see drastically higher compression motors, 10.5:1 is still a "high enough" compression ratio to see benefits at start and idle condition utilizing a better grade fuel. I am not saying to run the car with the higher octane fuel...I am merely saying that it is a good possibility that the feeling is real in regards to the smoother start.

DETONATION...look it up
thats the ONLY reason to use a higher octane fuel...
thats why we have higher octane fuels, not because they can give better mileage or make the car run smoother or start easier... Fuels DONT WORK THAT WAY
Higher octane is available at the pumps because some engines are forced induction, some engines run high compression ratios like todays modern Super sport bikes and off road bikes. Even some of these engines running 12.5:1 compression only require 87 octane

I hear what your sayin...
I'm just sayin NO, its not possible to start easier. Besided the compression ratio there is compression rates and HEAT... you need to calculate the HEAT of combustion into that mix... sure the lil yota engine may be a higher compression ratio then many other auto engines but at 10.5:1 there is not enough heat and compression at start up to take advantage of the higher octanes higher flash point..
My cammed Suzuki GSX750F pushes 100 hp runs 11:1 compression and redline of 12,000rpm and only needs 87 octane... Do you really think the Yaris needs better fuel then my crotch rocket?

Like i said it all has to do with the fuels flash point, the lower the flash point the easier it will ignite, the higher the flash point the harder it is to ignite.
Thats why many bio deisel set up have a deisel start because the biomixtures like used engine oil of veggie oil often has a much higher flashpoint and is harder for the engines to start on them. they start on the diesel and then switch over to run on bio once warmed up.

With higher octane fuels they not only have a higher flash point making it harder to ignite but they also contain additives that eliminate or remove free radicals in the fuel that can promote detonation. While the actual burnt temp of the fuel may not be changed the flame front speeds can be altered or slowed to help eliminate detonation. If you engine has no detonation, then there is NO benifit to running higher octane fuel... NONE

people often think higher octane fuels burn hotter and faster then lower octane fuels... this is a myth, actualy the lower the octane the faster it ignites and can burn faster depending on the additive and free radicals in the fuel..
If you were to take a carbed engine with fixed timing and diid two runs on a dyno one with 87 and one with 91 octane fuels. the 87 will always produce more HP and higher EGT (exhaust gas temps) then higher octane fuels...

Do you know why it feels smoother on higher octane fuel... they call this soggy. When an engine is jetted too rich or running too rich it has a soggy feel to it. An engine that is running a little to rich will run awesome, but it lacks power. the richer it is the less power it makes. And ebgine running leaner produces more power, too lean and you start to run the risk of overheating and detonation and pre-ignition ( not even close to the same thing bTW)
When an engine is running efficiently it can have what is known as spark knock or PING under heavy loads, this is normal but the more efficiently the engine is burning the fuel and the more power its making the less smooth it can feel.
Thats why racers often say the engine is a little lazy or soggy feeling when running rich or loading up. This is usually caused by an eninge that only needs high octane pump fuel but is being run on race gas.

[The little red pill]

. . . . . ouch . . . :slice:

[427chev]

I am not disagreeing with what you are saying. My point is that it's possible for the car to start smoother due to the higher octane fuel because, even though you may build engines and see drastically higher compression motors, 10.5:1 is still a "high enough" compression ratio to see benefits at start and idle condition utilizing a better grade fuel. I am not saying to run the car with the higher octane fuel...I am merely saying that it is a good possibility that the feeling is real in regards to the smoother start.

Nothing you said makes sense.

First of all, small chambers (inherent to a small displacement engine) are more efficient than larger ones because flame propagation occurs over a smaller area. That's the main reason that motorcycle engines are able to run such lofty compression ratios.

Secondly, the Yaris is one of the few engines that offers DIRECT INJECTION - which cools the intake charge and as discussed in the following link:

http://www.greencarcongress.com/2009/04/gms-expanding-gasoline-direct-injection-engine-portfolio.html

10.5:1 is not a high compression ratio for a modern, direct injected, small displacement engine. The 2.4 liter, direct injected GM engine discussed in the link above runs an 11.4:1 CR!

Hence, the 10.5:1 compression ratio in the Yaris engine (where each cylinder represents a mere ~ 0.375 liters and where direct injection is involved) isn't comparable to an engine that utlizes port injection and larger cylinders (particularly the bore dimension).

What amazes me about these bulletin boards is that people voice opinions without having any REAL understanding of the subject matter, most of which boils down to advanced engineering principals.

There is absolutely, positively NO EMPIRICAL EVIDENCE supporting the notion that any modern engine that has a recommended fuel octane rating of 87 PON can, in any way, benefit from a gasoline of a higher octane rating. If anything, empirical evidence suggests the opposite, since the slightly lower burn rate of the higher octane fuel may adversely impact the intended timing of the complete combustion process, relative to the position of the piston and the valves.

[jambo101]

Well said 427chev,i think most people fall into the marketing hype of naming the higher octanes with such colorful names (Super,deluxe,Premium,Gold etc)as to make 87 octane seem inferior,so they only fill up with that superior high octane and talk themselves into believing that they are somehow getting more power and better fuel economy without ever doing any meaningful measurements of whats really going on .

[DerFlosser]

Nothing you said makes sense.

First of all, small chambers (inherent to a small displacement engine) are more efficient than larger ones because flame propagation occurs over a smaller area. That's the main reason that motorcycle engines are able to run such lofty compression ratios.

Secondly, the Yaris is one of the few engines that offers DIRECT INJECTION - which cools the intake charge and as discussed in the following link:

http://www.greencarcongress.com/2009/04/gms-expanding-gasoline-direct-injection-engine-portfolio.html

10.5:1 is not a high compression ratio for a modern, direct injected, small displacement engine. The 2.4 liter, direct injected GM engine discussed in the link above runs an 11.4:1 CR!

Hence, the 10.5:1 compression ratio in the Yaris engine (where each cylinder represents a mere ~ 0.375 liters and where direct injection is involved) isn't comparable to an engine that utlizes port injection and larger cylinders (particularly the bore dimension).

What amazes me about these bulletin boards is that people voice opinions without having any REAL understanding of the subject matter, most of which boils down to advanced engineering principals.

There is absolutely, positively NO EMPIRICAL EVIDENCE supporting the notion that any modern engine that has a recommended fuel octane rating of 87 PON can, in any way, benefit from a gasoline of a higher octane rating. If anything, empirical evidence suggests the opposite, since the slightly lower burn rate of the higher octane fuel may adversely impact the intended timing of the complete combustion process, relative to the position of the piston and the valves.

What amazes me about bulletin boards is that they somehow produce these attitudes where people assume that other people are oblivious and what they say is the gospel. As cool as you might be, I also have an engineering degree to my credit...and 2 other degrees to boot but that doesn't mean shit. Engine dynamics are pretty involved but fuel is a fairly easy thing to understand. Octane, as you know, refers to a fuel's tendancy to explode rather than burn. A low octane fuel will will burn more violently, releasing it's power/energy sooner than a higher octane fuel while a high octane fuel is more stable, and burns more slowly or energizes at a slower rate. Higher octane fuel can result in a smoother start and idle(more stable and efficient energy). As far as gas mileage goes....there are thousands of opinions and real life proof that higher octane fuels can deliver better mpg's. For example....here is a blurb from good ol' Tony...

http://www.fuelsaving.info/fuels.htm

[darkmoon87]

I love how I started the thread asking about the "smoothness" and the thread turned into a gongshow arguements about MPG and power gains...sigh lol

[CrazedEpidemic]

I experience a noticeable gain in MPGs from 87 to 93

Thats what happened to me when I went to a Shell station that only had 93. I noticed more MPG.

[DerFlosser]

I love how I started the thread asking about the "smoothness" and the thread turned into a gongshow arguements about MPG and power gains...sigh lol

I agree....and the only point that I ever really "tried" to make is that it's definitely possible and not "placebo" that it starts and idles smoother. :iono:

[dybbuk]

And 427 seemed to be agreeing with you. However, he also said that smoothness was actually bad for the vehicle. Personally, I don't know much about engines (I am NOT a mechanic), but, I can read. It seems you guys aren't reading each other's arguments. It comes down to that it seems; yes, on higher octane fuels it will run 'smoother', but, it will also generate less power.

[2009Toyotoad]

I run 91 every once in a while, and it does feel smoother starting, accelerating, and idling.

Could it be a placebo affect? Maybe
Is it only a 2 dollar placebo, if it is? Yes


With the octane specific argument aside, aren't their cleaners and additives in 91 that aren't found in 87 at some gas stations??


Bingo! We have a winner. Big oil figured out a long time ago that to charge a premium price you need to create a positive preception that the vehicle "just seem to" run smother or more powerful when spending the extra $.10 to $.20 a gallon.

Some oil companies even figured out that they can package the stuff and give it fancy names like "Octane boost, Techron, or fuel system cleaner."

Now there is nothing wrong with buying or using these products. These products do clean the system of carbon crud. However, you can get almost the same effect from running WOT on 50 miles of back country road.

Since some of us don't have 50 miles of WOT roads nearby, these additives are a reasonable substitute.

Just don't fool yourself!

[427chev]

And 427 seemed to be agreeing with you. However, he also said that smoothness was actually bad for the vehicle.

Show me where I stated that "smoothness is bad for the vehicle."

I NEVER stated that. Please don't put words in my mouth again.

... It comes down to that it seems; yes, on higher octane fuels it will run 'smoother'...

Please produce third-party empirical evidence to support your claim that higher octane gasoline will cause a modern engine that's designed to run on regular gasoline to "run smoother."

Good luck finding that.

Have you ever heard of the "power of suggestion?" That's what's responsible for any "improvements" that are being claimed in using premium fuel in a Yaris. Objectively and empirically speaking, there are no ACTUAL improvements.

Medicine routinely demonstrates this phenomenon in what's known as "the placebo effect." People "feel better" when they eat a pill that made of compressed flour, for example, as long as the researchers tell the study group that it will make them feel better.

[nerp]

Yeah, it's placebo.

[jkuchta]

The Yaris DOES NOT Have Direct Injection. Direct injection is when the fuel in injected directly into the combustion chamber through an injector (usually a piezo injector) mounted in the roof of the combustion chamber. The Porsche LMP2 car has a direct-injection gasoline turbo engine, while both Audi and Peugeot run direct-injected turbo-diesel engines in LMP1.

The yaris does have indirect port injection (the injector is mounted just behind the intake valves in the intake port)....and in my testing does see gains from higher octane.

When running premium fuel (91 octane here in Cali.) I see more ignition advance than when running regular.

Octane only pertains to a fuel's resistance to detonation, and has nothing to do with flame front speeds, temperature, or the quality of it's burn (i.e. clean or dirty).

The yaris ECU is designed to run a minimum octane of 87 because it has enough range of adjustability to pull timing out to stave of detonation. Running higher octane will allow the ECU to run a more aggresive timing map, making more power.

[07WYarisRS]

yeah we no it will allow it to advance the timing more
BUT why does it advance the timing? What is it that tells the ECU it needs or can go with more timing?

The engine MUST advance the timing more because the 02 sensors are picking up incomplete combustion from too high of octane and a rich air/fuel ratio...
by advancing the timing it creates more heat to help with more efficient combustion...
this is what I have been sayinall along....
the overall power remains the same because the advanced timing is just countering the effects of the overly rich mixture that would be reducing the power output.

Thats why I said if you ran them both in an engine with fixed timing the lower octane will always make more HP, in order for the engine thats running high octane to make the same power you must change the valve timing and ignition timing for more compression/different overlap and earlier spark for a more efficient combustion...
This is why when i'm setting up race engine we start out rich, watch the EGT and CHTs as well as power output. Then start leaning things out. if the CHT's spike but EGTS drop the engine is starting to detonate. if a higher octane is needed we usually have to adjust the timing as well to bring the power back that we lost.

But thanks for proving my point

[PHXDEMON]

I run 91 octane and add 2 bottles of chevron octane booster into each tank. Needless to say I run 13's at the track :bow:

[ChinoCharles]

I love how I started the thread asking about the "smoothness" and the thread turned into a gongshow arguements about MPG and power gains...sigh lol


Never been on a car forum before? :laugh:

Save yourself the money and run GOOD 87. If you want to do your engine a favor, BUY GOOD GAS. People will go to Korner-Mart and buy 93 and say "hey, look at me... I'm concious." You're not. Just buy good, basic gas... 87 from Shell, Sunoco, etc. Its a Yaris people... not a Bimmer.

[jkuchta]

yeah we no it will allow it to advance the timing more
BUT why does it advance the timing? What is it that tells the ECU it needs or can go with more timing?

The engine MUST advance the timing more because the 02 sensors are picking up incomplete combustion from too high of octane and a rich air/fuel ratio...
by advancing the timing it creates more heat to help with more efficient combustion...
this is what I have been sayinall along....
the overall power remains the same because the advanced timing is just countering the effects of the overly rich mixture that would be reducing the power output.

Thats why I said if you ran them both in an engine with fixed timing the lower octane will always make more HP, in order for the engine thats running high octane to make the same power you must change the valve timing and ignition timing for more compression/different overlap and earlier spark for a more efficient combustion...
This is why when i'm setting up race engine we start out rich, watch the EGT and CHTs as well as power output. Then start leaning things out. if the CHT's spike but EGTS drop the engine is starting to detonate. if a higher octane is needed we usually have to adjust the timing as well to bring the power back that we lost.

But thanks for proving my point

That's an interesting idea...but a little out in left field..the ECU is programed to run the most advanced timing it can get away with without detonating...that's why the timing is more advanced with the higher octane.
The reason you would want to run the timing as advanced as possible is that it will lead to higher cylinder pressures, which equal more torque.

The octane rating of the fuel has no bearing on the mixture setting, other than the fact that with a more knock-resistant fuel you may be able to run a little leaner without problems.

[07WYarisRS]

That's an interesting idea...but a little out in left field..the ECU is programed to run the most advanced timing it can get away with without detonating...that's why the timing is more advanced with the higher octane.
The reason you would want to run the timing as advanced as possible is that it will lead to higher cylinder pressures, which equal more torque.

The octane rating of the fuel has no bearing on the mixture setting, other than the fact that with a more knock-resistant fuel you may be able to run a little leaner without problems.


the ECU pays more attention to ther F/A ratio to control the engines timing then the KNOCK sensor... you get better mileage and long engine life by controling the engine fuel/air temps and engine temps then controling just knock...besides your not going to get knock at 1/4 throttle or slow cruise speeds or low rpm operation.

So let me get this strait if I add an octane booster the bumps it up 4 points 87.4 octane because of the additives that reduce knock to as much as a 91 octane it will max out the timing to the highest possible timing and the cheapest octane booster on the market will magically give me more HP because the ECU only listens to the knock sensor for when to alter the timing...
Well my racers use 100+ octane in thier race bikes so I guess i better start running that because then I will make the most HP out of all ya'll
yeah i don't thing so.

[07WYarisRS]

http://www.youtube.com/watch?v=2jbcCr2ll3c&feature=related

here is the perfect example, higher octane when not needed actually reduces HP
I'll never argue the FACTS when talking about increased compression and forced indiction, i have built many engine N/A and boosted.
Sure these cars can and WILL see power gains when using higher octane levels that will allow an engine to run at higher boost levels without knock. BUT these cars were designed to run higher octane fuels, but made to accept low octane as well.

but we are talking about a stock Yaris here and economy car designed to run on economy fuels for the best bang per buck per mikle and the quesion is if the higher octane gives any mileage or performance gains over 87
87 will give you the best MPG in this econo box

[ChinoCharles]

^^ Use 87 or 07WYarisRS will find you while you're sleeping and cut your brake lines.

[jkuchta]

http://www.youtube.com/watch?v=2jbcCr2ll3c&feature=related

here is the perfect example, higher octane when not needed actually reduces HP
I'll never argue the FACTS when talking about increased compression and forced indiction, i have built many engine N/A and boosted.
Sure these cars can and WILL see power gains when using higher octane levels that will allow an engine to run at higher boost levels without knock. BUT these cars were designed to run higher octane fuels, but made to accept low octane as well.

but we are talking about a stock Yaris here and economy car designed to run on economy fuels for the best bang per buck per mikle and the quesion is if the higher octane gives any mileage or performance gains over 87
87 will give you the best MPG in this econo box


I didn't see anywhere in that video where they played with the ignition timing to take advantage of the higher octane.

PLUS...

this thread is about higher octane fuel, not additives.

[TheSilkySmooth]

our engines are NOT high compression... my street bikes run 200psi plug per cylinder and run on 87 octane... guess what they have less then 10:1 compression ration.

The ECU will not re-tune for higher octane...
The only time it will make a difference is if the engine is knocking... then the knock sesor will pick up the engine knock and retard the timing.. it won't change the fuel maps to compensate.

Spark knock AKA PING is completely normal and just means the engine is running efficiently...

running a lower octane fuel will reduce carbon built up as it has a lower flash point and will burn more efficiently and completely... Also start running a TRUE synthetic like Amsoil or Redline with no mineral oil or by products that cause deposits to form and after 10 years you engine will still be 95% carbon free So 10:1 in the Yaris is NOT high compression? BAH! 2) The ECU is CONSTANTLY adjusting the fuel trim for proper running as required!
3) How do you know if the timing is in retard (without a scan guage) on WOT?

All that said, I usually run regular. If the engine is healthy, and NOT carboned up, it should run OK on 87PON. I think I cooked my cat#1 from driving too hard and have to get it replaced with the high flow ( for free!?) on the TSB EGO35-06 .... Car is feeling lazy and getting choking sulphur smell in the cabin when I whomp on it:frown:

[07WYarisRS]

No 10:1 is not high compression, not nearly enough for high octane fuel...

I know this thread is about high octane fuel but whats the differenece between 87 and 91 octane? really? Additives or lack of that neutralize or remove free radicals in the fuel the promote detonation.
There is no difference performance wise between a h91 octane fuel and an 87 octane with a 7 point octane booster added, Both will resist knock the same amount.
Thats all there is to higher octane fuel...nothing more. Its resistance to uncontroled combustion... there is no HP gains to be had unless your engine is running forced indiction or compression to high for 87 octane... the YARIS does not have too high of compression for 87

I know the ECU is constantly working to control "proper running" that why it has oxygen sensors and a field of others.
Some want us to belive that the ECU listens to the knock sensors to control the timing.
Others like myself belive that the ECU use incommming air temps and volume, F/A ratio, VVT & rpm and TPS to control the engines power/fuel delivery and timing for the most optimal combustion. Add in all these factors and you won't see any performance gains from higher octane fuel

[TheSilkySmooth]

We are lucky since the yaris has advanced yamaha designed cyl heads, and small bore/long stroke (undersquare) which would reduce the chance of detonation. But cars with large dia pistons like a subaru 2.5L would be more prone to knocking - so they employ intake tumble generators and EGR to get the autoignition temp down. But in an absolute sense 10:1 is high compression. In my book I make the cut at 9:1 high to low. If you rate 3 categories: high middle and low for RACE, I would say 10:1 is middle for Gasoline. Then you have distinctions for alky and Diesel which is a whole nother enchilada ...

[TheSilkySmooth]

I'm sick of people saying the yaris is "only 100 HP" This is a VERY high state of tune for a street motor under warranty. Not as high as an old VTEC Integra/Civic, but if it was a 5.0 mustang in the same tune, it works out to 350 HP! (calc: 5.0L is 3.33 times the size of 1.5L yaris X 105hp.)

[ROCKLAND TOYOTA]

I think I cooked my cat#1 from driving too hard and have to get it replaced with the high flow ( for free!?) on the TSB EGO35-06 .... Car is feeling lazy and getting choking sulphur smell in the cabin when I whomp on it:frown:

WRONG, your cat was doomed from the start. HENCE the TSB from way back in the begining of 2008....

[TheSilkySmooth]

WRONG, your cat was doomed from the start. HENCE the TSB from way back in the begining of 2008.... Whadya mean - its doomed to fail and just a matter of time b4 it clogged? RockToy - Does the TSB concern the #2 cat further back, or, the #1, Or the pipe in between? Sorry for all the Q's. You think they will give me a hassle(the old melted grocery bag story) ? or is there a back pressure test that it would show up on? Thanks for the help man:smile:

[Nudger]

89 and 91 octane wow!! thats so low. I usually use 95 put perfer to use 98 with 10% ethnol

[Yaris Hilton]

You're looking at Research Octane Number. It's established in a special low speed engine with cold air intake and a low operating temperature. There's also a Motor Octane Number that's much more reflective of fuel performance in real world automotive engines, but it's a considerably lower number. When the US required posting of octane numbers at the pump, the various involved parties couldn't agree on which number to post, so they compromised on the average of the two, R+M/2. It's actually a meaningless number as the "sensitivity" or difference between the two numbers can vary substantially, so one "87 pump octane" gasoline may knock more easily than another.

[liyux2k]

the engine is already running at max specs with 87. what ever better fuel you put in just going to force the engine to wear more in order to burn it since the compression stays the same. is not going to boost performance or mileage, the only thing it does is more wear towards the engine. ;)

[SilverGlow]

Only idiots put high octane gas in a itty bitty Yaris motor...they say they "feel" the difference...all BS....higher octane means higher flashpoint, meaning LESS POWER, LESS TORQUE, LESS MPG...LESS CLEAN COMBUSTION....

Leave the 91 octane to motors truly need it like high compression engines, turbo engines, super charged, many BIG displacement engines, etc....only boy racers with one foot still in the sand box swear by 91 octane....all that money wasted...it adds up after years of stupidity....

[borezack]

Hello first post here.

I have an 08 sedan.

Just would like to know if I should change from using 85 to 87.

I'm driving at 3000 to 10000 ft elevation and regular here is 85, plus is 87 and premium 91.

Also Just took a trip and was about 200ft above sea level and I used 87 since that was regular and my car felt like a rocket ship lol

Just would like some input.

Thanks

[2009Toyotoad]

Hello first post here.

I have an 08 sedan.

Just would like to know if I should change from using 85 to 87.

I'm driving at 3000 to 10000 ft elevation and regular here is 85, plus is 87 and premium 91.

Also Just took a trip and was about 200ft above sea level and I used 87 since that was regular and my car felt like a rocket ship lol

Just would like some input.

Thanks

This is probably a question best answered by a local Toyota dealer. They should have the best knowledge on local conditions and fuel qualities.

[borezack]

There is no local Toyota dealer here. The closest one is over 130 miles away.
Will 85 octane damage the engine?

[schleppy]

87 octane is the lowest recommended isn't it? I wouldn't go lower than that, esp. at higher altitudes.

[twowheels]

+2 lol :thumbsup: i used to get 60 miles before the first bar went, now i use 91 it goes up to 75-80 on the first bar =), i wasn't satisfied with 60 miles on the first bar

I'll call your anecdote and raise you one...

I always run 87 and almost always get 90+ miles from the first bar w/o topping off.

[mryaris]

Will 85 octane damage the engine?

No. 85 octane is used in locations with high altitudes because it behaves like 87 does at lower altitudes/sea level. I live in Colorado and regular is 85, mid is 87 and premium is 91.

So.....to clarify a bit, high altitude 85 octane= the 87 octane that all the low-landers use, so using mid-grade 87 is not necessary.

[SilverGlow]

As the altitude goes up, the requirement for high octane goes down.

[Forrest]

With the cost of gas going up so quickly, yesterday, May 29th it was 2.60 for 87 and 3.00 for highest oct., I would stick to the recommended gas at the lower price.

[ImportRacer88]

when i first got mine i ran preimum once and the car ran like shittocky mushrooms and when i went to fill up i put regular back in it and it ran better so i just been running reg had no probs here but im moving back to pa has ne one had any probs woth thier CAI in the snow pm me and let me know

[borezack]

OK thanks for the info

[Yaris Hilton]

How far you go on the first bar depends heavily on how full you fill the tank. I run the pump fast till it clicks off, wait a few seconds, start it back at a trickle and let it click off again. (It barely puts in a dollop of gas the second time, but it makes for a pretty consistent fill without overfilling.) I usually get close to 100 miles on the first bar.

[voodoo22]

We've never put in anything other than 87 octane. We purchased the Yaris to reduce travel expenses and given it's performance over the first 79 fill ups 87 octane suits it quite well.

We do only fill at top tier stations though.

[Thai_Dang]

91 octane will make your penis larger. yeah i've also read anything above 87 is harmful for your engine. Makes sense, these cars have sensitive timings. But i can't imagine with how many computer chips they put into these cars nowadays, that the ECU would detect the 91 octane that some idiot put in their car and adjusted the timings of fuel injection so it doesn't cause engine knock/build-up.

[ddongbap]

HOLY THREAD REVIVAL.

[frog13]

Compression dictates octane

[yarrr]

HOLY THREAD REVIVAL.

ya its kind of his thing if you hadn't noticed. I think maybe his "new posts" button reads "old posts" and he can only see the oldest posts on the forum.

[10peep]

HOLY THREAD REVIVAL.
:laughabove: I just spent 35 minutes reading this pissing contest so I absolutely HAVE to make some kind of comment to revive it. You ready....? Here it is.........comment.



"......Thats why many bio deisel set up have a deisel start because the biomixtures like used engine oil of veggie oil often has a much higher flashpoint and is harder for the engines to start on them. they start on the diesel and then switch over to run on bio once warmed up......."

^^^ This is wrong, btw. Biodiesel setups usually do not have any type of diesel start or diesel purge setup because biodiesel is made by the user from WVO. On the contrary, WMO/WVO setups almost always have a diesel start and diesel purge setup because the viscosity of the "fuel" (WMO/WVO) is MUCH higher than the viscosity of ordinary diesel until it reaches temperature (usually around 180deg) and will very quickly clog up one's entire fuel system if initiated before it reaches optimum temp. Consider this thread revived and maybe now we can discuss something MUCH cooler than octane ratings, smoothness and high/low compression engines....DIESEL!!!!

[Idahotom]

Speaking of diesel: I was at a gas station in SE Idaho the other day, fueling up my 22 ton boom truck. I was astonded to see they were offering straight diesel ($3.86 per gallon), off road/non dyed (and you do NOT want to get caught with that in your tank) for $3.64, and lastly bio diesel for $3.86. The owner of the station must be a diesel freak! As everywhere else was elling diesel for $3.97 or higher, I was a happy camper.

A few days earlier, while also fueling the boom truck, I struck up a conversation with a VW Jetta driver: 47 to 49 MPG, and he had over, well over, 200,000 miles on it. Without even doing the math (in general higher priced diesel V. gasoline) the Yaris compares well...( in the low 40's, my own results) plus I trust Toyota more then VW!

[10peep]

Speaking of diesel: I was at a gas station in SE Idaho the other day, fueling up my 22 ton boom truck. I was astonded to see they were offering straight diesel ($3.86 per gallon), off road/non dyed (and you do NOT want to get caught with that in your tank) for $3.64, and lastly bio diesel for $3.86. The owner of the station must be a diesel freak! As everywhere else was elling diesel for $3.97 or higher, I was a happy camper.

A few days earlier, while also fueling the boom truck, I struck up a conversation with a VW Jetta driver: 47 to 49 MPG, and he had over, well over, 200,000 miles on it. Without even doing the math (in general higher priced diesel V. gasoline) the Yaris compares well...( in the low 40's, my own results) plus I trust Toyota more then VW!

NICE!!! Yeah, its hard to even FIND off road Diesel here in VA, much less without any dye in it. Its SO funny you mention a VW diesel... I was ON MY WAY to the stealership to BUY a VW diesel that I had ALREADY test driven a couple days earlier but I had read SO many bad things about EVERYTHING other than the motors on these cars that I just didnt feel comfortable doing it. I figured that Id swing by the local Carmax to see what they had first walked right PAST the Yaris that I actually ended up going back and buying 4 days later. Went across the street to the VW, Subaru place and some guy came in with a diesel Jetta and couldnt say enough about how much of a turd it was and thats all it took for me. Went across the street to the Toyota joint, test drove a new Yaris (on my wife's suggestion, because she saw the one at Carmax :biggrin:), went back to Carmax and bought mine for $5k off of sticker with 12k miles on it. :thumbup:

[The Spectacle]

I'm digging this up from the dead rather than creating my own thread because I'm sure it would just spiral down the same road.

I've just filled up my tank with 89 after 3 years of nothing but the 87 and there is DEFINITELY a difference in throttle response and midrange power. I'm still a bit shocked myself but its there.

I read through a few of these responses and its clear that not many of you know how knock sensors and timing retard/advance work. That's all well and good but I just want to state for the record that Yaris behaves slightly different if you put higher octane in it.

[Flipper_1938]

Hello first post here.

I have an 08 sedan.

Just would like to know if I should change from using 85 to 87.

I'm driving at 3000 to 10000 ft elevation and regular here is 85, plus is 87 and premium 91.

Also Just took a trip and was about 200ft above sea level and I used 87 since that was regular and my car felt like a rocket ship lol

Just would like some input.

Thanks

Probably had more to do with the denser air than the fuel...

[ROCKLAND TOYOTA]

I'm digging this up from the dead rather than creating my own thread because I'm sure it would just spiral down the same road.

I've just filled up my tank with 89 after 3 years of nothing but the 87 and there is DEFINITELY a difference in throttle response and midrange power. I'm still a bit shocked myself but its there.

I read through a few of this responses and its clear that not many of you know how knock sensors and timing retard/advance work. That's all well and good but I just want to state for the record that Yaris behaves slightly different if you put higher octane in it.

im SHOCKED it took you 3 years to fill up with something else!!!

WELCOME to the club and when you get to the last few bars on the guage you'll notice they don't disappear as fast.....

[The Spectacle]

Yaris is my daily driver and my other car is 400whp+ so I have never really bothered. But curiosity got the best of me so I gave it a shot

[Flipper_1938]

For shits and giggles, I filled up with a tank of premium.

....and I did get better mileage.

My normal in mixed driving is 40 mpg. On this tank, I got 43 mpg!

But with the added cost of premium ($.20 per gallon/ $2.00 per tank), it is pretty much a wash.

I am going to see what happens with 89 octane (mid grade) on the next fill up.

[A-Dingo-Ate-My-Baby]

I'm digging this up from the dead rather than creating my own thread because I'm sure it would just spiral down the same road.

I've just filled up my tank with 89 after 3 years of nothing but the 87 and there is DEFINITELY a difference in throttle response and midrange power. I'm still a bit shocked myself but its there.

I read through a few of these responses and its clear that not many of you know how knock sensors and timing retard/advance work. That's all well and good but I just want to state for the record that Yaris behaves slightly different if you put higher octane in it.

this may be because 3 years of carbon buildup on the pistons incrementally increases compression, therefore if you are having the knock sensor retard timing...higher octane will reduce that somewhat... which translates into smoother power. 3 years of buildup is just a thin layer but will increase compression [and small carbon chunks also create points for detonation to occur]. minor overall effect but that could be the reason for smoothness. still won't go any further down the road with higher octane, but I bet it can smooth the power delivery. if you wind on the yaris all the time there will be less carbon, or if you seafoam it, or use bg44k, that sometimes makes carbon chunks flake off and they get burned up at the cat...but by far the best thing is pull the head and use direct solvent or steam on the pistons, that removes carbon. [of course you are looking at a lot of work for an incredibly minor issue.]

[The Spectacle]

I disagree. I don't think it has anything to do with carbon buildup...takes 100k+ for that to be any type of issue. I might have 40k on the car.

I attribute the change due to a very sensitive knock sensor and some very conservative timing maps from Toyota for 87 octane. I'm averaging about the same MPG, as on 87...but I the car drives so much better that don't really care.

[comk4ver]

I'm going to revive this old post as well. I started noticing a shake during idle with my foot on the brake. When I took it to the mechanic at 70,000 miles he said, it weird that you're complaining about a shake in the car since your spark plugs are good for 100,000 but I changed them. What gas do you use, I told him BP the lowest one. He said that recommends Chevron and to use the high end stuff. So I did, but that was like three years ago? I looked at the manual today while the car was refueling and noticed that the manual says 87 or better.

Sent from my VS980 4G using Tapatalk
http://uploads.tapatalk-cdn.com/20160925/849c3a9d8beb0b9a5c5de056df999736.jpg

[comk4ver]

About three years ago my car was shaking at stop lights with my foot on the brake. When I took it to the mechanic, he looked at it and said if it did again to come back and change the spark plugs. When it did it again, he said that I was crazy because the spark plugs were manufactured to last up to 100,000 he changed them out at 70,000. He also asked me about what gas I used I told him BP 87. He told me to switch to Chevron 91. So today, I was running out of gas when I HAD to use Shell. I got the lowest one, I decided to pull out the manual... Does that mean that the engine can adjust without negatively affecting the car?
57532

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[bronsin]

Probably.

My Honda ST1300 motorcycle calls for premium in the OM and on stickers near the fillup. But it runs fine on regular and the computer automatically adjusts the timing to prevent knock.

MAny of us ST1300 owners have ridden to northern Canada where premium is rarely found and we have no problem running using regular. In fact the majority of us dont use premium at all.

I DID use premium in my Yaris once and the next morning there were TWO of them in my driveway! :bonk: Apparently it released the Higgs Boson in my engine, causing it to get pregnant. :bonk:

:laugh:

[holly01]

http://juragan.club/7/g.pngsubscribed, this seems like a very interesting thread

[ern-diz]

This is such a fuzzy topic of discussion for me.

There are those that swear 91 is better for your engine than 87 is. Then there are those that swear it is not. There are those that claim 91 is only for high compression, performance engines, while others say the 1NZFE actually runs at a pretty high compression (10:1, or something??).

I used 91 for the majority of my Yaris' life and switched to 87 more recently. Can't say I noticed a difference. I don't mind paying more and I don't mind paying less - what I do mind is doing the wrong thing for my engine.

I wish there was more of a consensus on what fuel we should be putting into these cars.

[Idahotom]

Put regular in it. Or premium or if it makes you feel better! All mine has ever gotten is regular. I don't waste 2 seconds worrying about which to use. ESPECIALLY at my altitude over 4500' ASL. My kitplane engine builder tells me to use mid range or premium if at sea level, but as most of my flying is at 4500 and way above, he told me to use regular, and he is a professional mechanic highly respected in his field. Around here its 35 to 50 cent a gallon difference, I have better things to spend my money on then gas meant for a higher compression engine.

[WeeYari]

I wish there was more of a consensus on what fuel we should be putting into these cars.

Every consumer watch dog type of report will state using premium where regular is stated is throwing money away. The big gas companies are great at marketing the premium fuels as being superior regardless of the octane recommendation from the manufacturer. Of course they are. Look at the profit margins inherent in the price differential. In Canada, this is approximately $.20 per liter.

[tmontague]

The Yaris does run a relatively high compression but is tuned to not knock with 87 octane and is what is recommended by the vehicle guide.

Most higher performance cars that call for 91 can be run on 87 and not knock due to knock sensor which will result in retarded timing and less performance.

If the Yaris had a tuning map programmed in the ecu from factory then it would definitely be a difference running 91. That said if the Yaris had that map it would be advertised by Toyota. Toyota isn't going to tune a 91 octane map on a NA sub compact economy car.

The reason you get better fuel efficiency with 91 is that most 91 rated gas has no ethanol in it.

I ran 87 in the 370z I rented while in Mendocino on my honeymoon. The rental company said that's all they put in them ever regardless of it calling for 91. I hammered that car for 3 days on mountain/canyon runs and it had no issues other than less power than 91 fuel.

If a car has no 91 octane tuning map then you cannot take advantage of the advanced timing and more power you get from it.

You will however get better fuel efficiency (I know I do) but as Wee stated above, with 91 octane being $.21 /L extra it ends up costing more in the end.

Drive your car on the highway once a week, keep up with the maintenance including preventative and don't be afraid to go WOT every few weeks. You engine will be clean as can be and you only ever have to run 87oct.

I personally don't notice a difference in performance really switching to 91 other than better fuel efficiency.

That said I drive my car pretty hard every couple days and average about 5.6L/100km so I have no interest in 91oct.

[ern-diz]

That all makes sense, thanks.