Here is testament to Marvel Mystery Oil I thought I would share, for both the supporters and haters of MMO on this forum: In the 1960s and 1970s, my grandfather was an 18 wheeler owner/operator, often driving cross country. He routinely got 1 million +! miles between rebuilds simply by always using 20% MMO and 80% engine oil. Of course this included regular recommended oil and filter changes, and engine tune ups. Keep in mind that this was during a time of greatly inferior oil base stock and detergent quality. When the engines were finally gone through they were amazingly clean, stuff of legend among mechanics in the area. Discuss.