Do You Need to Pay for Premium Gas?
Pull up to a gas pump and you’ll see several options, presented in a row with an ascending price per gallon. Whether regular (87 octane in most states), midgrade (89), or premium (91 to 94), your choices are differentiated by an Anti-Knock Index (AKI) octane rating. That’s a measure of a fuel’s resistance to causing engine knock, which occurs when fuel in the engine ignites unevenly or at the wrong time. It makes a “knocking/pin...