I read the original Popular Science article in 1976 that featured Mobil-1 on the front cover. They'd tested the oil in a vehicle, ran 100,000 miles, ran another vehicle using conventional oil with recommended oil changes. The Mobil-1 was never drained, but the filter was changed at regular intervals, and oil topped off as needed. Then came the engine teardown, along with the required photos. The cylinders in the Mobil-1 car still had visible hone marks. Valve stems were clean, as were the valve covers. Conventional oil car...not so good. Caked up sludge on the valve stems, pockets of sludge throughout the engine. Actually...it looked pretty good...but the Mobil-1 engine looked amazing.