mazdadrifter

higher octane fuel is more refined and is less resistant to combustion without a spark



87 octane makes your car faster because it essentially advances your timing.... the fuel combusts quicker and begins the powers stroke sooner, but if your already advancing your timing a lot with 93 octane, then 87 octane could possibly lead to detonation.



89 octane is simply a blend between 87, and 93 octane, if that particular gas station's "mixture ratio" is off, then you might have had more like 88 octane.



I say just stick with 93/94 octane, and tune your car more aggresively.

1971ChevelleSSV8

Octane is simply an anti-knock rating, which basically 'controls' how fast your compressed air/fuel in your engine burns with the spark. The higher octane you have, the slower your fuel will burn, and therefore be less efficient with less power (may even negatively effect your gas mileage). When you mixed the octanes you probably did have equivalent to about 91ish octane, so your fuel could burn quicker, which means better response, more power, and more efficiency.



Basically, the idea for best performance is to adjust your timing and find your engine's 'sweet spot'-the lowest octane you can run (for best performance) on the best timing curve without pinging. If you need ping a lot then go up in the gasoline's octane, if a bit just try some octane booster. You should also test the optimal octane you can run at WOT because you'll lean out and ping up there on WOT/high RPMs, which is obviously bad as well.



For a piston engine it is hard, because there are a lot of factors to making a high-powered engine on lower octane (like cam, piston type, cylinder compression, combustion chamber size/shape, ignition, quench, etc), but for a rotary (I'm not positive on this) it seems there isn't 'as much' to worry about (though detrimental effects to pinging are worse in rotaries from what I can tell).



My summer project will be building the highest horsepower engine I can on the lowest octane possible. If I had the money I could probably put down 500HP to the wheels on only 89 octane, N/A. Then again, that's if I had truly unlimited funding, which I don't, and if I was putting down 500hp to the wheels I'd probably blow my non-performance 3-speed automatic pretty quickly Oh, this is power out of a small-block Chevy V8, too.



The whole octane thing I just talked about did apply to N/A engines, yes, but it is still the same in a boosted engine, because of the compression factor. What I said would still work in a turboed engine, but only at the specific amount of boost used. If you up the amount of boost your turbocharger is putting in, you're obviously gonna have to go up octane a bit because of a higher compression.



Got questions or if this was unclear, I can answer them, kind of doing 2 things at once when writing this and may not make sense.

pengaru

if you get more power and no pinging when you go to less octane it sounds like your car just has alot of safety margin tuned into it.



which you may or may not like, up to you. if you want more power, increase boost and/or advance timing a bit more. Being turbocharged, you can take advantage of greater octane (more boost!).

j9fd3s

thats why if they run out of 87, you get 92-93-94 for the price of 89, they usually have a tank of 87 and a tank of 93-94, and it gets mixed on the way to the pump

vosko

that is how the gas station i worked at did but 2 tanks of 87