Here is a link that talks a lot about sprint engines and fuel:
Sprint Car Engines
Don't confuse the Ethanol in E10 and E85 fuel with Methanol used in racing. E85 will give you about 25 to 33% less mpg than old 100% hydrocarbon fuel. E10 will give you about 3.5% less mpg.
Many racers use straight Methanol, simply known as alcohol. The engine tuning is important when switching fuels. You can't set up your engine to run on street premium and start using Methanol and expect optimum results. The correct A/F ratio would be much different between the two fuels. Also, Methanol based fuel is very corrosive and would need to have correct fuel system hoses and gaskets to last.
Most of the country has 92 octane or better octane available. California switched to 91 premium because of an
oil company patent lawsuit and the 91 premium spilled over to Arizona and Nevada. Just about all of the fuel across the country is 10% Ethanol or E10. Ford actually claims more HP in their F-150 when running E85. You can't always tell when you are getting E10 because some states (CA) don't require the pump to be labeled as E10.