I plan on doing a UOA in a couple weeks, but when I filled up the motorhome (1990 E350 about 10,000 pounds plus, 460 V8 with 69,000 miles) with Maxlife 10w40 last week, in my zeal to rid myself of some stuff, I put in 15 oz Rislone Winter start (never to buy again as it is merely synthetic oil, prob Gp III) and leftover 8 oz STP Oil Extender. A few days later started kicking myself as it will affect the UOA, but now I am thinking it should not matter as I suspect the 6 qts Maxlife will dominate (7qt capacity with oversized filter). The thing is, I am going on a trip and won't have another UOA opportunity till Oct (only vacation in off season--the season of the "newlyweds and nearly deads"
). So unless you convince me otherwise I plan to UOA this stuff.
OK, that said, the other question is at what mileage to sample. The trip promises to be minimum 4000 miles, but possibly up to 5000. (Detroit MI to Glacier Nat Park and back.) Book says 3000 mile change for severe service which has 6 points, of which I fit maybe two. I have run this with no apparent problem on 5w30 for 3800 miles before, so I am inclined to run it to 4000, sample and drain, but if it looks good on the stick, I may go the whole distance.
[ April 29, 2004, 12:06 PM: Message edited by: TallPaul ]