Changing Octane

[geoff5093]

Last time when I changed from 87 octane to 93 (premium) octane, my mileage dropped from around 20 to 16mpg, but I didnt even notice any difference in power or pickup. And to make sure I filled up again using 93 but still didnt notice any difference.

I know there have been a few threads out there, but is there any real benefit to go to 93 if its had 87 for pretty much the entire life of the car?

[RningOnFumes]

No use really.

Unless you develope some sort of knocking, kicking up to a higher octane may help, but other wise you're wasting money as the 5sfe doesn't really utilize higher octanes to increase permance at all (stock engine)

[geoff5093]

Originally Posted by RningOnFumes

No use really.

Unless you develope some sort of knocking, kicking up to a higher octane may help, but other wise you're wasting money as the 5sfe doesn't really utilize higher octanes to increase permance at all (stock engine)

I dont have the 5SFE. If you look in my sig, I have a V6 (1MZ-FE).

[toyomoho]

A good test is if the engine pings. Some engines will not tolerate a lower octane fuel and let the owner know this when going up any kind of hill. Others have carbon build up that result in pinging if lower octane is used. If the engine runs fine on lower octane no need for a higher grade.

[geoff5093]

There hasnt been any pinging or knocking using 87. So I guess i'll save myself some money and keep buying 87.

[s_ajanthan]

There are casing when the 1MZ-SE will knocking but thats generally only when go up mountains at high altitude. No point in wasting your money with higher octane when regular will do. I really hate people filling there cars with premium when they drive something like a corolla...

[Mike Gerber]

"I really hate people filling there cars with premium when they drive something like a corolla..."

The oil companies love it. That's how they make extra profit; selling consumers something they really don't need. As the others have said, if your engine doesn't ping on 87 octane, you will see no improvement in either performance or mileage by switching to either 89 or 93 octane.

Mike

[Saleen Owner]

Originally Posted by geoff5093

I know there have been a few threads out there, but is there any real benefit to go to 93 if its had 87 for pretty much the entire life of the car?

There is no power gain in octane alone. If your car is designed to run on 87, you will actually get less power out of 93 octane fuel. You have proven this to yourself in lower fuel economy, or better stated, lower engine efficiency. You only need higher octane with increased cylinder pressures, like from advanced cam timing, milled heads or a turbo or supercharger. Even then you are not getting more power from the higher octane fuel, only reduced detonation at higher cylinder pressures.

[ASG14]

There is a SLIGHT bump in power under full throttle on my 1MZ with 93. But most of the time I use 87 as it does just fine.

[Toysrme]

Octane is a measure of how stable the fuel is. The more stable it is, the less power it has. By using more octane than the car was designed to use, you're lowing power output, and grossly increasing emessions.
The only time more octane would really do anything, is if your engine was suffering from pre-ignition. Which is generally nothing more than needing a good cleaning.

[ASG14]

^ Ok, you REALLY need to search and RESEARCH this before you even touch your engine. There is a lot of disscusion on it. As well as several VERY good write-up's by Toys on it.

[Blackhawk3D]

With a turbo installed regular octane will ping at any kind of pressure.

[geoff5093]

Originally Posted by ASG14

^ Ok, you REALLY need to search and RESEARCH this before you even touch your engine. There is a lot of disscusion on it. As well as several VERY good write-up's by Toys on it.

lol, lucky for me im not doing it alone

[Toysrme]

Not nessiceraly. There is already 14.7psia in the intake manifold to begin with. 5psi of boost would simply be 19.7psia in the intake manifold. The problem with pre-ignition is due to the rise in charge temperature, and the mild increase in combustion chamber temps. You want higher octane as a preventative measure even if you don't ping.

N/A 87octane VS 10psi 87octane VS 10psi 93octane would round about be changes of:
The average combustion chamber temeprature from 4497*F-4627*F-4629*F when tuned for peak power. The key, is not tuning it for peak power, and keeping the charge temperature low by using effeciently matched compressors, and means of post cooling afterwards.

For compairison, the stock TRD blower @ 4.5psi with the correct fueling (hahahaha) would achive average temps at 4594*F. and would be about the same level of predisposition to knocking. Why? Because the blower gives maximum gains at it's lowest rpm, and highest load; where a turbo will generally provide from the midrange on. Where the load, and knocking is slightly less pronounced.

[Toysrme]

Which is a good example why when tuned fairly well Tony's original CT26 setup @ 10psi trounced the shit out of the TRD roots blower power wise at any measureable relavant rpm you'd like to compair them out. All-the-while being abit safer to run.