Illflem, and others - thanks fo the data. I'll get some Napa's, after all that's where I get my new oil for my ISB now! But if you look at my recent post on oil, I had to go through gymnastics to get it from NAPA. I now have 110,000 on my 2001 and I have been using the Premium Blue 2000 (which was a blend), and had a vis of 15-40. I had 8 quarts of it and went to get another another case from Cummins Northwest and found that Valvoline stopped making the blend! So I called Valvoline and was put on to this new oil.
http://www.valvolinehd.com/onroad/blue2000.html
I've always liked synthetics and the guy told me (we talked for 20 min) about this new full synthetic. He essentially convinced me it was the next best thing to sliced bread - and I'm not to easy to convince. He also told me that NAPA was selling it at a great price - less that $12/ gallon! I didn't like the 15w-40 for winter starts at all. I live in western Wa, where the cold isn't severe, but I do travel into cold country, and didn't like the cold starts with this vis of oil - so the new full syn is a 5w-40 and fully backed by Cummins! I seem to be converted to this approach - now I need to decide if I still change at 5,000 miles, or go to say 7,500 or 10,000. I could easily change the filter at say 5. 000, but not sure it's that full at that point anyway. And I know I could send off for an oil analysis, but at some point it's just as easy to change the oil. I'm not looking at a 20-30,000+ change interval - I simply doen't think it's possible to get rid of condensation etc without changing the oil -
I don't want to get into an oil war - but a lot of guys use bypass filters, for extended drain intervals. I'm not interested in that at this time, but I did note that this new oil passed the 100,000 extended drain interval using I'm sure some great filtration.
I do use the Fleetguard Strat's for my ISB.