Favorite Gas for your IS?

[Kurtz]

Originally Posted by MiiK350

I ran out of gas(91octane) at THE PURSUIT(irwindale dragstrip) while racing, and the only gas they had was 110 octane, and I consistently ran .3-.5 faster then any of my previous runs.

(Don't mean to get off the topic of favorite gas, but my 2cents of the on the on going discussion)

In what car, and what were your times (posted timeslips before and after on the same day would be nice).


Given that all the fastest known NA 2ISes in the world ran their times on regular pump gas, and you as the previous posters fail to offer any explaination for how or why higher octane fuel, which doesn't in and of itself contain any additional energy or in any way enhance power, could produce more power I suspect your story won't end up being quite as illustrative as you suspect.


(BTW, assuming this was even in a 2IS, I sure hope you checked if the fuel was leaded or not... a lot of race fuel sold at tracks contains lead, which will do significant damage to a few components on your car)

[Kurtz]

And just to save you guys some time, here's a decent, non-Wiki, explanation of what Octane actually is-

http://auto.howstuffworks.com/fuel-e...question90.htm

The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.

That's it.

resistance to knock.

That's the only thing octane level indicates.


So you should -always- use the lowest possible octane that causes no engine knock.

Which for a 2IS is 91.

Anything higher is a 100% waste of money because it's not doing anything else

Anything lower will cause engine knock, which besides being bad, which cause the ECU to pull timing and reduce power.

But once you're running high enough octane to not have any knock (again, that's 91 for a 2IS) anything higher does nothing for you, because the only thing it CAN do is avoid something you've already avoided.

There are many changes you can make to an engine to produce more power (raising the compression ratio, adding some sort of forced induction, advancing the timing, etc) and THOSE changes can cause the engine to produce more power, and those changes can then require a higher octane fuel to avoid the engine knocking. Here again the only thing the higher octane is doing for you is resisting the knock that might otherwise be caused by the _other_ changes you made to the engine.

If you're making no such changes than the higher octane can not do you any good, because the only thing higher octane fuel does differently is resist knock better. If the motor isn't knocking to begin with the "extra" octane does nothing.


Claiming higher-than-needed octane "makes your car faster" is akin to claiming adding a second volume knob makes your radio louder. What you already had is already doing all it needs to.