Fuel does not stay fresh forever. Gasoline begins to oxidize in a few months, forming sticky varnish and gum that can clog carburetors, injectors, and fuel filters. Diesel faces its own problems: as ...

Back in 2004, several automakers got together to create a more pure form of gasoline to meet strict standards set by the U.S. Environmental Protection Agency (EPA), now known as Top Tier gasoline.