According to GM, the typical motor oil drain interval is 8,500 miles in GM vehicles equipped with Oil Life Systems, while the average drain interval is 5,000 miles in competing vehicles.  In addition, the company foresees drain intervals topping 30,000 miles with minor engine modifications and appropriate motor oil quality and 40,000 miles with major engine modifications.  "But we still need to strive for the best fuel economy, no compromise on engine durability, and no negative impact on emissions systems," says James A. Spearot, director of GM's Chemical & Environmental Sciences Laboratory in Warren, Mich.  Amsoil Synthetic motor oils offer superior protection for extended drain intervals of up to 35,000 miles without the need for engine modifications.

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