Retailers selling Top Tier gasoline sell the highest quality gasoline available on the market as certified by seven major automakers. These retailers include many major gas station and supermarket brands, including Costco, Chevron and ARCO.
Top Tier gasoline is certified by a consortium of automakers that consists of BMW, General Motors, Honda, Toyota, Volkswagen, Mercedes-Benz and Audi. These fuels contain high-quality additives that are intended to keep deposits from building up in engines, as such deposits may eventually damage car engines and shorten their service lives. Top Tier ratings are not related to the octane ratings for gas, so it is not necessary to buy premium-grade gas to gain the benefits of Top Tier gasoline.