Everyone likes to save money on car expenses, especially fuel. But cheap no-brand gas may not contain enough detergent additives to keep your fuel system clean. Major brand gas may cost a few cents more per gallon, but it can help prevent expensive fuel system repairs down the road and give you better gas mileage today. The formulation of fuel also changes from winter to summer, you can expect a 10% drop in fuel economy in the winter. You might also experience running problems when the fuel starts to change in the spring or fall.