From the QT web site: "Our convenience store gasoline guarantee is even stronger: if your car has a fuel-related problem, bring the statement from your mechanic and we'll pay for the repair. Our convenience stores make this promise because it's the right thing to do. For a company so dedicated to quality, how could we NOT have a guarantee so strong?" I buy gas from TopTier providers Shell (through the Circle K stores), QuikTrip, and Phillips 66. Does your car like QuikTrip gas?