Since 1995, all gas in the US is required by law to contain a minimum quantity of deposit control additives to help keep engine components clean, resulting in lower emissions, improved fuel economy and better power in the vehicle.
But in 2004, as engines had already evolved significantly, six automakers (GM, BMW, Toyota, Honda, VW, and Audi) began to recommend higher levels of additive. They felt the current EPA minimum deposit control requirements did not ensure optimal engine performance, especially given their ever-advancing engine designs. These automakers came up with a new standard for gasoline with greater deposit control performance. This higher quality gasoline standard is known as TOP TIER.
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