I'm an "old time" mechanic. I started using Marvel Mystery
Oil back in 1958. I joined the US Air Force in 1961, while using the additive in my Ford with a fresh rebuilt engine. After 170,000 miles, I decided to "upgrade" to a larger , more cube engine. I sold my old engine which had good compression to a friend. No problems. Some time donw the road my buddy had to replace the
oil pump, he told me the inside of the engine looked like it was rebuilt yesterday. NO sludge, no varnish, no dirt!! He said it was a pleasure to work on iT. You figure!!