Well I'm at a good mileage to do a UOA with the QS, so I think I will and post the results. I have to confess though, I was picking up a couple of motorcraft filters for the truck and found M1 10w-30 in the 5 quart jugs for $14.88. Obviously I couldn't pass it up, so I picked up two of them. I was actually thinking of using it in my girlfriends 98 beetle (which has some major sludge issues) to clean it out a bit. Instead I may keep it for my truck and give her car an AutoRx treatment. The 0w-40 looked tempting, but I read here that it slips out of grade quickly and loses TBN fast. Somebody posted that UOAs proved that the life of it was only about 5000 miles. Of course for my drain intervals, that would be fine. What about D1 5w-40? Does anyone think that would be a bad choice in a truck that specs 5w-20? The 40wt in the M1 and D1 scare me a little.