Studies have been conducted which illustrate the excellent overall performance of a synthesized passenger car engine oil during greatly extended drain intervals. These studies were conducted primarily with automobiles manufactured in the U.S. and with typical U.S. service. Supporting data are presented in areas of engine cleanliness, engine wear, and lubricant stability from several types of service conditions including heavy duty taxicab and police car operations as well as typical everyday consumer driving. Information is also provided from a high mileage test using the EPA durability cycle. These field test results correlate well with extended duration API SE sequence data.