[LetsRok]

If I am paying $3.19/gal for 93 octane, am I getting 93? If not, I want a refund from the vendor. The pumps at my local 7-Eleven say "Contains 10% Ethanyl"

[xzins]

I don't think Octane equates to BTU.

Octane, by definition, is the resistance to burn or detonation. The higher the rating, the slower the burn when ignited during the compression burn cycle of the piston. The higher octane allows for better control of burning for high compression engines. So we want to match the correct octane rating of the gasoline to the engine design to ensure complete burning of the gasoline by the engine for maximum fuel economy and clean emissions. http://theserviceadvisor.com/octane.htm

[Yo-Yo]

Octane rating is the resistance to detonation under compression, it is not a measure of the amount of energy per unit volume.

93 Octane gasoline must be used in a higher compression engine to prevent knocking. 93 Octane gasoline used in an engine rated for 87 Octane is a pure waste of money.

[Eric in the Ozarks]

You're getting the 93 octane. If your fuel is 10 percent alcohol, the base gas is probably 89 or 90 octane and the remainder comes from the alcohol.
When 10 percent ethanol gasoline first became popular, the oil company I worked for developed a subgrade, 85 octane straight gas to accomodate the alcohol and not exceed 87 octane at the pump.

[SAJ]

Octane, or more properly ''octane rating'', is an inverse measurement of the resistance of a given substance to combustion. Thus, a higher octane rating translates to ''burns more readily''.

Ethanol's octane rating is 105-110 (iirc). So, gasoline (hexane-heptane) blended with ethanol will by definition have a higher octane rating than that same gasoline without the blending. You're getting your 93, don't worry about it.

You're also getting moderately worse MPG. 10% ethanol is bad enough, but E85 has to be the biggest joke of a fuel in modern history.

Well, except for hydrogen.