Schaeffer Manufacturing Co. 9003D-012S Supreme 9000 Full Synthetic Gasoline Engine Oil 5W-30, 1-Quart Bottle

Customers report that the engine oil performs exceptionally well, running smoothly and improving gas mileage by 5-10%, with one customer noting they can go 5,000 miles between changes without needing to add more. They appreciate its quiet operation and cleanliness, with one customer mentioning their engines last longer. While some customers find it worth the premium price, others consider it expensive.