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. The advantages are it’s sustainable and burns cleaner than fuels that are purely petroleum-based. The disadvantages are you might get lower fuel economy and a recent study has shown that the land-use aspects of growing corn are carbon-intensive. Should you use this gas instead of regular 87 octane or does the potential to cause damage to your car’s system outweigh the savings at the pump?