回复：回复：If car needs 1 qt oil every 500 miles, it probably

Unfotunately,that is not true. Used oil at certain mileage actually protect engine better than the new oil. By the way, I did a simple calculation. For the examlp of engine needs one qt oil every 500 miles, the average oil life will be about 1300 miles after 5000 miles, and reach a average life of 2000 miles after 10,000 miles from a new oil change and stay at 2,000 miles until next oil change.