It depends on the type of race car you are talking about. For example:
- NASCAR engines burn 110-octane leaded gasoline.
- Indy cars burn pure methanol (a.k.a. wood alcohol, CH3OH).
- Top Fuel dragsters and funny cars burn nitromethane (CH3NO2).
Each of these fuels has advantages and disadvantages. For example, the methanol fuel used in Indy cars has the advantage that it can run at extremely high compression ratios (meaning more power -- see How Car Engines Work for details). Methanol also has a nice safety feature -- you can extinguish a methanol fire with water. 110-octane gasoline also handles high compression well. Nitromethane is basically a liquid explosive and contains a great deal of energy per unit volume (more than twice that of gasoline).