I took my car into the dealership a couple of weeks ago to get a tire replaced (nail too close to sidewall). They comped the new tire, washed the car and filled it with gas (not sure if this is a GM thing or a dealership thing, but I appreciated it). They told me anytime I bring the Volt in for service they wash and fill it. Today I noticed the engine icon stays on. The owners manual calls it the "Malfunction Indicator Lamp" and says that it could be either bad fuel or the gas cap is on wrong or something more serious. I checked the gas cap and tightened it another click, but now I am wondering if they pit either bad fuel in the tank or low octane fuel. Either way I am taking it in today and getting another free tank and a wash. This time I will make sure it is 93octane.