OK, Octane and heptanes make up the 2 major components of gasoline, 87 = 87 parts Octane and 13 parts Heptane and so forth. The Heptane component provides combustion, but can easily ignite under compression, so cars with lower compression can use a mixture such as 87, but cars with high compression need 90 plus. If you are running a modern vehicle with a high compression engine and computer based ignition system, it will retard the timing to reduce knock, which in turn is basically reducing compression and finally reduced horsepower, this is a fact. How much power? I don't know but if you put it on a dyno you would see.

Airplane fuels still contain lead, so they put in an additive called TEL so this is a different rating system just in case someone ask why AVF is higher than 100.