You might have noticed that some gas stations occasionally offer specials on unleaded 88 octane gas—also known as E15—which contains 15 percent ethanol. Ethanol is an alcohol that’s derived from corn.

Car Craft has been doing tech stories on E85 fuel longer than any other performance-car magazine. By now it should be well known, but in case this is news to you, E85 is an alcohol-based fuel blend of ...