While the majority of types of gasoline on the market today contain only the minimum amount of cleaning agents required by government standards, Shell says that isn’t enough. According to Shell, gasoline meeting, only minimum requirements can leave harmful deposits on engine parts. Additionally, four leading automakers, BMW, General Motors, Honda and Toyota, are so concerned with declining gasoline quality, that they recently created the ‘Top Tier Detergent Gasoline’ standard to help keep vehicle engines cleaner and reduce deposit-related problems.