The Schaeffer oils are some of the longest lived oils available. I know salesmen who drive clunkers and the lab has them on 10,000 mile oil drain intervals with that Schaeffer oil. In a good engine it is good for 12,000 or more. It is the lowest cost per mile of any oil I know of, and keeps the engine clean with reduced wear. I use the 10W-30 in my turbo Volvo, and I think the boost gauge is climbing faster with this oil.
Ken