Just filled up the tank with 91 octane premium fuel

[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]

Originally Posted by 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.

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]

Originally Posted by ham

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]

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!

[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]

Originally Posted by 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.

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]

Originally Posted by 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!

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]

Originally Posted by ham

I experience a noticeable gain in MPGs from 87 to 93

i agree with you

[jambo101]

Originally Posted by ham

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]

Originally Posted by ham

I experience a noticeable gain in MPGs from 87 to 93

+2 lol 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]

Originally Posted by 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

Not only could it be, it is.

"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]

Originally Posted by Aothachos

+2 lol 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]

Originally Posted by 427chev

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.
.

[427chev]

Originally Posted by 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."

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/...ature/(page)/1

http://www.consumerreports.org/cro/c...l-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]

Originally Posted by 427chev

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......