A fuel quality standard known as Top Tier has been in existence for over two decades. It was developed by major automakers, including General Motors, BMW, Honda, and Toyota, due to concerns that federal minimum detergent requirements were not sufficient to protect modern engines.

Top Tier is a voluntary standard that is backed by 11 major automakers. It contains higher concentrations of detergent additives to prevent carbon buildup. Both AAA and Consumer Reports recommend seeking out Top Tier fuel.

Further information about Top Tier fuel, including where to find it, is available from TopTierGas and other sources.