5-30 Mobil 1 every 5K miles, but now every 10K miles. 144K miles on engine. When I had the valve gaskets replaced, the BMW dealer tech said that's the cleanest engine he has seen. 5 qts of Mobil 1 at Walmart for about $26, like one post said sometimes they are on sale.
Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid. Albert Einstein
Swim upstream. Go the other way. Ignore the conventional wisdom. If everybody is doing it one way, there’s a good chance you can find your niche by going exactly in the opposite direction", Sam Walton.