Esmanolo

Hello,



Has anyone fun 100 octane unleaded gasoline in their Sq5's ?

ELEVENS

Octane rating is meaningless without knowing the method used to calculate it, or at the very least, the country. It would help if you updated your profile to contain at least your country.

apohis

The higher octane rating won't do much unless there is a different engine fuel and timing map to go with it.

Esmanolo

My apologies, Im in the US.
100 Octane unleaded is from the pump at gas station.

ELEVENS

I will help in really hot weather or under hard, hard running when the knock sensors would normally pull timing advance. Other than that, it would only serve to drain your wallet.

sdiver68

You do know higher octane fuel has less power potential, right? 100 octane may actually reduce power in an engine designed for 91.

Coolieman1220

doesn't most 100 and 110 octane fuel contain lead?

acadianbob

Lead additives are illegal. Have been for about 40 years . . .

Xenonista

It's the other way around. The octane refers to the number of chemical bonds, and more bonds = more chemical energy. However, they're also harder to break in the first place, which in practical terms means a higher compression ratio is required, or the fuel will only be partially combusted. (The exhaust will smell like farts or popcorn.) Lower octane can be used by retarding ignition until after peak compression has been reached, and it's decreasing. What's counterproductive is running higher octane than the peak compression ratio and combustion speed calls for.

The octane rating is only an average. If you mix 87 and 96 you get 91.5. However, the 87 components will be prone to ignite earlier and the 96 components later. This yields worse performance (slower propagation) than a more pure 91.5. 100 octane race fuel is very narrowly 100 octane, so even if the compression ratio would indicate it's subpar and can't be fully combusted, it can actually work better than the "right" octane.

sdiver68

Well I might have oversimplified but I assure you the additive package often used to raise the octane rating do in fact reduce energy content. And the rest of your post is full of misinformation. Here's a good guide to gasoline, http://www.turborick.com/gsxr1127/gasoline.html