higher octane fuel

[KSIbucky]

Can a higher octane hurt a car (spark plugs) just wondering. I know some people that think they can ho faster and do all this stuff cool amazing stuff (fly, go back in tiime, end world hunger, and fight polio) with that magic 93 octane.

[spkrman]

seems to boost my top end and give better mileage when driven hard... same 300 mile trip with 87 and 92 got 32 and 35mpg respectively, both were mostly 80 with some sprints to 100... although I was a little more conservative with the 87 it still got worse mileage.

[acrbill]

If it was any other car I would say that it would hurt mileage and power. For those who don't know, the higher the octane the slower the fuel burns, so basically you want the lowest octane you can get away with for max power.

This car has 10.5:1 compression though. The ecu must set the timing really low to get the car to run on regular gas. You have to wonder how much power is being hidden by the 87 octane tune. You also have to ask yourself if the ecu could adapt to 93 octane and give you more power.

In my old Neon it recommended premium fuel. You could put regular fuel in but mileage and performance would suffer.

[captainzerocool]

I have seen a noticeable improvement in mileage jumping to 89 from the 87 octane.

[acrbill]

I have seen a noticeable improvement in mileage jumping to 89 from the 87 octane.

I am going to give 89 a try for the next fill up.

[Black Yaris]

I think I am going for an octane upgrade next fill up as well, has anyone tried an octane booster aditive?

[acrbill]

I think I am going for an octane upgrade next fill up as well, has anyone tried an octane booster aditive?

Don't bother with that junk. Just mix in some higher octane with the regular if you feel the need.

[Black Yaris]

I never realy tried an octane booster, just wondering if anyone has...

[acrbill]

putting additives in your tank can sometime mess up the sending unit. I put a few cap fulls of Marvels Mystery oil into my Neons tank and it read 3/4 after a fill up.

[PetersRedYaris]

I'm not big on fuel additives. I did however get better mileage with 91 (premium here in SD) octane fuel but didn't record the exact numbers.

[nsmitchell]

For what it's worth, I paid the extra 20 cents per gallon ($2.00) for super unleaded (91 octane) yesterday. Since our engines have a fairly high compression ratio I figured I'd give it a go and see. Should I disconnect my battery to reset the ECU?

[daq421]

Someone put some hard numbers in this thread please. I'd love to know if the MPG increase (whatever it may be) actually offset extra 20 to 35 cents per gallon it would cost to run Super over regular unleaded..

-Peter

[07WYarisRS]

Higher octane fuel don't burn slower...in most cases burn rates are the same provding the fuel additives are the same in both octane fuels.... if they do it's because of additives in the fuel, ill get to that later. A higher octane simply means it has a higher flash point meaning it takes more heat and compression to ignite the mixture.
10.5:1 is not a high compression engine and does not require a high octane fuel. Sure it's a bit higher then many cars but many bikes have compression of 12:1 and still run 87 octane. A lot depends on the combustion chamber design, timing and fuel maps.

Octane boosters don’t really bump up the octane of the fuel
Most only 3-7 points witch is less then one octane level. Octane booster do however contain additives the remove or neutralize free radicals in the fuel that promote detonation and pre-ignition.

Because higher octane fuels have a higher flash point; meaning is it takes more heat to ignite. Higher compression creates more heat. So to avoid igniting the a/f charge prematurely you want something that has a higher flash point. If your engine don't have any problems with the engine suffering from detonation or pre-ignition you don't have to worry about using a higher octane fuel. it won't do anything.

Additives or lack of, in the fuel can help to increase or decrease the burn rate slightly as well. Running a higher octane fuel in of itself will not increase HP. This is a myth.
Rule of thumb is only run the amount of octane needed to prevent detonation or pre-ignition of the fuel. Run anything over that and there will be a loss in power as the fuel/air mixture is not able to burn completely.
Black smoke or carbon collecting in the exhaust tip is a sign of a rich mixture and/or the engine not being able to burn all of the fuel completely. Runnning a higher octane then the engine needs or was designed to run can and often will shorten the life of the polution control system (cat convertor and oxygen sensors)

Think about it...why design a econo box if it requires or performs better on the most costly fuels available....
Stick with the 87 or if you are hauling a heavy load or lots of passengers bump up to an 89

[eTiMaGo]

Interesting read... I wonder if the engines here are tuned differently, as 91 octane is the lowest you can get, as well as 95...

[spkrman]

duno, better top end and better mileage for me... I don't think the 2-3mpg increase I've seen offsets additional cost.

The manual doesn't say you can't run 93, it says run at least 87.

As far as any dyno's I've seen, higher octane fuels increase power?

[johnnyfive]

Interesting read... I wonder if the engines here are tuned differently, as 91 octane is the lowest you can get, as well as 95...

i belive it is just a differance in how the octane is rated, i cant remeber any details on it..but i do belive that your lower octane is an equivilent to the north american lower octanes...

[jaspie]

I find it strange ~ That you guys are talking about 87.....89.....91.....93 octane fuel ~

Here in Australia we have 95.....98 and 100 octane fuel ~ I fill up with 98 octane fuel and there is quite a big difference with the regular fuel ~

That's my opinion anyway ~

Jaspie ~

[Yarii]

North America measures octane differently than the rest of the world so it's numbers do look lower. That said, I'm pretty sure american 87octane is slightly lower than the average regular in Europe. Probably why (or because) european cars have high compression rates, and american cars run a pathetic inefficient 8.5 or 9:1.

[Kaotic Lazagna]

for some reason, when ever i used 91 (supreme) gas in my GTI (when i had it) and my father's Camry, the mpg dropped a lot. both cars normally use 89 (plus) gas. that's why i never bother to put anything higher than 87 (regular) in my Yaris. oh yeah, we've always used Chevron.

[cleong]

So does anyone know why the American continent uses a different octane yardstick from the rest of the world, because over here, like eTiMaGo and jaspie, the lowest octane I can get is 92, and thereafter you get 95, 98, and 98 with special additives.

Australian 100 octane is really a lower octane petrol mixed with ethanol that raises its octane number, without really improving the performance as you'd expect a straight 100 octane would.

In my old car which was a carby Toyota 4A-FC engine, and my friends' EFI 3S-FE Camrys, we found that going 98 octane yielded about a consistent 10-20% mileage improvement.

[jaspie]

I see ~

But if calculate is it worth it ~ I think it is.....though I haven't done the calculations ~

The 98 octane in Australia is 6c more than the regular fuel ~ 6c more doesn't make a big difference in the total price for the Yaris and having the 4c discount receipt ~ ^_^ ~

Jaspie ~

[cleong]

I used to be from Brisbane. I recall at least at Coles Express - Shell, 98 was 10cts more costly than regular unleaded.

You only need to calculate fuel cost per in terms of cents per kilometre to work out which fuel is cheaper to use.

For me, 98 was the most economical fuel. Between 92 octane and 98 octane, I was seeing a 150km difference per tank, and it only costs $5 more.

Take note however, that my carby motor was a "dumb" motor that doesn't change its timing to suit the fuel (I think).

Some people say that with modern engines don't benefit much from running premium fuel though. I'm still on my first tank with my car, so I'll be finding out. I'm on the middle ground using 95 octane currently.

[swng]

The following extract from an article on Encyclopedia.thefreedictionary.com (Wikipedia Encyclopedia, see link below) explains why quoted octane numbers seem to be higher in Australia and Europe than in North America:

"In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in the United States and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, would be 91-95 (regular) in Europe."

Here is the whole article: http://encyclopedia.thefreedictionary.com/octane+rating

Hope you like it:smile:.

[mikeukrainetz]

Fuel octane doesnt make power, it allows you to run higher compression rates which does. Youd be hard pressed to find a car made in the past ten years which runs anything less than 9:1. The reason we can get by with as low as 87 octane with 10.5:1 compression is the major advances in computer controlled management, head / valve design, chamber quench design, timing and fuel delivery. The whole idea is to prevent detonation, higher octane fuel means more cylinder pressure / higher temperature before detonation happens. Its kind of like adding antifreeze to coolant to allow the water to boil at a higher temperature.
Since the yaris CAN run on 87 at 10.5:1 there is not real benefit to running higher octane unless you bump up compression. You wont get any more power because the compression doesnt change. You may however be able to adjust the timing a few degrees - on my old v8's advancing the timing to the point of detonation would sometimes net upwards of 20-30hp on stock heads on regular pump gas.

10-20yrs ago most any north american four cylinder would be lucky to make 80hp, a lot of them in or around 50-60hp. Goes to show what improvements have been made in engine design.

The only vehicle I run premium in is my '70 chev with a high comp. small block with old school cast engine and heads - cause I have to.

[cleong]

Last two posts have been very informative. Thanks guys.

[swng]

Last two posts have been very informative. Thanks guys.

Internet is great:smile: :smile: :smile:!

[mikeukrainetz]

just an addition to actually answer the original question. No the fuel you buy at the pump no matter the grade will not harm your plugs, in the Yaris anyway. Spark plugs run in a temperature range - the length of the electrode. Lower compression hotter the plug, higher compression cooler the plug. The plug is meant to remove heat from the cylinder - higher compression produces a lot more heat so the plug needs to run cooler so it doesnt cause pre-ignition or detonation from too much heat retention. Its kind of a fine line but just know the more performance, compression etc your engine has the cooler the plug youll need to run.
So since the plugs are already meant for high compression they wont get damaged in the least.

[jaspie]

Oh I see ~ Thanks guys ~ Very helpful to know.....it's great to know about other Yaris drivers around the world ~

I'm calculating the 98 octane now and how much more economical it is ~ I'm only half way through my tank ~

I've only used regular fuel once.....the first tank when the dealer's gave me a free full tank ~ That averaged around 6.7L/100km ~

Jaspie ~

[07WYarisRS]

Oh I see ~ Thanks guys ~ Very helpful to know.....it's great to know about other Yaris drivers around the world ~

I'm calculating the 98 octane now and how much more economical it is ~ I'm only half way through my tank ~

I've only used regular fuel once.....the first tank when the dealer's gave me a free full tank ~ That averaged around 6.7L/100km ~

Jaspie ~

mikeukrainetz is right on the money.

Y should not start to calculate your fuel mileage yet.....
The engine will have changed slightly between the first two tanks as it was broken in and will continue to loosen up the more miles you put on it. I tight engine runs quiet and has a bit higher resistance, wait a few months until the engine and drive line have all worn in and loosened up for the most accurate readings.
My car gets better mileage now with 25,000km on the odometer then it did when it was new.

The iridium spark plugs, stock on the Yaris engine work well and you will never have a problem with them. The iriduim plugs allow them to remove more heat faster the standard copper plugs or even platinum plus and this allows them to maintain a slightly higher heat range that keeps the plug clean and resists fouling while still providing the same cooloing as a copper core of a much colder rating. Add to the the fine wire design firing tip and dence metals resist errosion and provide sharp crist edges for far better spark performance over a much longer time. (150,000 km+ vs 50,000 using standard plugs)

[captainzerocool]

North America measures octane differently than the rest of the world so it's numbers do look lower. That said, I'm pretty sure american 87octane is slightly lower than the average regular in Europe. Probably why (or because) european cars have high compression rates, and american cars run a pathetic inefficient 8.5 or 9:1.


Low compression ratios isn't all bad. There are advantages to being able to run on dirt.

[captainzerocool]

The octane rating here in the states is nothing more than a anti-knock index. Hell, e85 has a very high octane rating but you make 30% less power and get 30% worse mileage.

[Impresive-G]

This is a very intresting thread. Though Im still a little bit confused.

My mom owned a 2000 toyota Camry 5psd MT, 4cylndr engine. She used to put on the fuel it neede but once started noticing trouble. One day she decided to put on 91oct. the camery ran better and gave more better gas miles. the car ran grate for the rest of the 4 years we had it.

On my previous car, my 240. All it neede was 87 oct. Car ran grate. Then everytime I went on a touge run i gave it some 91oct. Baby ran great and strong. I felt a lot more torqe and a goo power band response when i floored it. The gas did burn a bit quicker but thats probably because I was redlining it a lot and bouncing the rev limiter. But I did notice the remining 1/2 tank I had left after my run it lasted me a good 250 miles.


The thing that has me confused is when you said that high octane does not giv eyou more power. In a way I have to disagree, but probably because ive seen high numbers on tuned cars. My friends EVO9 runs at 276hp on 91oct. when he started to use 100oct the dyno showed an increas in hp. I dont have the graph but it did showed.

RC developments EVO 6 runs at 749hp on 98oct, 821hp on 100, and 930hp on 118.

Now help me understand of how this is a myth...

[07WYarisRS]

Why? because it's a turbo charged engine... a performance engine that is tuned to run on the edge may have the timing pulled slightly if the engine pick up any knock... higher octane = no knock. With a turbo charged engine a higher octane will help cool combustion temps wile preventing detonation and the engine can adjust the fuel trims for slightly more power.
But even then with a 300hp engine it may be a difference is 1-2 hp

On a 100 hp engine not designed with performance in hand but rather fuel economy higher octane won't do a thing except cost you more $$$ everytime you fill up.

Log the car over 6 months using 91+ and 6 months using 87
then calculate how much $$$ you spent of fuel and you will not save $$$ using higher octane fuel in an econobox.

FWIW cars like our Buick Regal GS 3800 supercharged, ZZP Eaton blower, pulley kit, cams, injectors, fuel pump, exhaust etc etc run fine on 87 octane providing you not pushing it to high boost levels. But pushing it requires higher octane otherwise the engine starts to knock and pulls the timing to prevent engine damage and that hurts the HP.

[Impresive-G]

Ah... I see.

[mikeukrainetz]

Some missunderstanding about this may come from its overly abundant use in auto publications where multiple aftermarket parts are tested over a range of gasolines to develop baseline performance figures. Its a lot more involved than just pumping gas - 07WYarisRS is correct and obviously has some (or probably a lot) of previous engine building / tuning experience.

This might make things slightly clearer - this info was taken directly from the Department of Weights and Measures in the US.


Don’t use High Octane Premium gasoline unless your car’s manufacturer specifically recommends it. In most cases, a higher octane will not improve performance or reduce fuel consumption. It will just cost more at the pump.

Facts To Consider About Octane
What is an Octane Rating?
Your engine burns a mixture of air and fuel that is injected into each engine cylinder. Octane ratings measure the ability of an automobile engine to prevent engine knock, which occurs when some of the air-fuel mixture spontaneously ignites too early, causing a sudden jump in cylinder pressure. High Octane gasoline burns slower. This reduces engine knock.

What is Engine Knock?
It is not unusual for an engine to make a “pinging” noise at full throttle, due to high cylinder pressures. Engine knock, however, should not be ignored because it could result in serious engine damage. NOTE: If your engine knocks or pings, it does not necessarily mean something is wrong with the fuel. It could be signs of problems with the engine’s electronic control systems, ignition timing or exhaust gas recirculation.

How is Octane Rating Determined?
Two different testing ratings are used to establish Octane Ratings
MOTOR METHOD: Gasoline is run through an engine under load.
RESEARCH METHOD: Gasoline is run through a free-running engine. This method typically gives higher octane ratings than the motor method.
NOTE: State and federal law require service stations to display the Octane Rating on their pumps, on a yellow label with black lettering. The rating displayed on those labels is an average of results from the Motor and Research methods.

Does High Octane increase engine power?
Not if your car is designed to run on regular.

Does High Octane gasoline improve gas mileage?
No. If your car is designed to run on 87-Octane gasoline, which is the minimum rating for regular, switching to high octane will not improve mileage.

NOTE: If switching to High Octane does improve mileage, it may mean that your engine, or its control system, need repair. Consult your mechanic.

How is High Octane Different From Low Octane?
High Octane gasoline burns slower. This reduces engine knock when cylinder pressure is high.

Can I switch from Premium to Regular?
Check your vehicle owner’s manual. If your manual does not specifically recommend High Octane you probably can switch. If the vehicle knocks, pings or runs poorly try the Mid-Grade before returning to High Octane fuel.



Just as a side note: If you have a car thats around ten years old you may notice it pings or knocks with the same type of gas youve used for years. Typical combustion creates byproducts which usually wind up being carbon buildup in the valves or combustion chambers. The carbon promotes detonation but if you were to run higher octane gas (provided the problem isnt major buildup) youll notice power increases and no knocking or pinging. Of course being a car thats ten or more years old means you may also have worn out ignition parts as well.....

[jaspie]

Actually......I was reading through my manual the other day ~

The Australian Yaris Hatchback Manual does say to use 91 and higher octane fuel (and or or?) ~ So I wasn't too worried about switching straight to 98 octane after my first free tank from the dealer ~

Jaspie ~

[nsmitchell]

I tried Premium and I saw 33MPG. That was mostly high speed highway. Nothing great, but it was worth the $2.00 extra to find out. :)

[calmcool]

About Octane it is the second truth story about why the North American can not get the high performance car and the other story would be the incidence that happen, the US car manufactures whose ask the government to protect their own products right in 1994 and deny high performance and high quality foreign products to cross the US border.

Low Octane fuel (87 Octane) are actually very bad fuel for ultra high performance engine such as high compression with high output or small displacement and high compression turbo engine with high output.
That why for the high end engine it requires at lease 92-94 octane, which is actually a recommendation from car manufactures.

97 octane is perfect for high performance street car but American don't get that because they prefer cheap gas.
And in some European and Asian country gas station. They offer 97octane and up to 102 octane!

But do not confuse a pure high performance fuel brand with the race fuel Methanol which is a compound of fuel that only offer for very special race engine application. And they are "very bad" for any type of street engine without saying that they are very bad for the environ. They also sale in Europe and Asian countries. And "yes" they are cheaper than the same grade of fuel.

87 octane fuel create more pollution and give poor performance than the premium grade fuel 94 octane.
The 94 octane give better performance and reliability to car owner and better mileage.
Today there is also the added Ethanol fuel and the 20% ethanol fuel.
They are part of the bio fuel but not exactly like the bio-Diesel fuel story.
It is a 9000-year-old Chinese invention and successful developed by the French for cars application.
This kind of fuel are even more "friendly for the environment" than any fuel that we use today. They give more horsepower too but cost more expensive than the same grade of fuel.