On a trip to South Dakota this past weekend, I rented a car and noticed a sign at the rental car counter advising against filling up the car with 85 octane fuel. So all weekend I wondered about this. E85, meaning 85% ethanol and 15% unleaded gasoline, is apparently becoming more common in the U.S. This is especially true in the midwest where corn is used for producing it. Ethanol has high oxygen content, burning more completely and producing less emissions. Corn converts the carbon dioxide into oxygen. So why would they advise against using it? There aren’t a lot of car companies that make E85 models. Most cars are fuel injected and using the lower octane will cause “knocking” and can damage the engine over time. To find out if your car can run on ethanol or find E85 fueling stations, check out the National Ethanol Vehicle Coalition website.