Well, guess I need to clarify myself. I do change oil at least every 10,000 miles. What I mean by atleast is how much work the truck had done in those miles. If I am hauling hay or anything else where I am working the truck hard (18,000lbs of hay on 24' gooseneck trailer), then I change the oil every 5,000 miles. But when I am doing strictly highway driving like I normally do, then I change it every 10,000 miles (or about once a month) whichever comes first. Yes, I do put around 10,000 miles a month on my truck, with my kids being on the east coast and me living in Oklahoma. I use wix filters, along with the Mystic oil, and use Lucas in my fuel just about every tank. The longer change intervals are not for everyone, I don't pull trailers often, and my daily commute is 80 miles one way on the turnpike, no stop and go traffic. I use mystic, one because it helps keep the American oil field going (no, this is not made from foreign oil as foriegn oil is a dry/sour oil and is only really good for gas). Two, I have had good luck with it on my tractors (both are diesels). Yes, the oil is made by citgo which is hdqtr'd in Tulsa.
Morph.