Someone posted a link to this thread on another site. Don't everyone go there at once and overload their server.
I thought it was some very interesting responses from a GM engineer regarding the use of synthetic oil and extended drain intervals. I'll still continue to use Mobil 1 and Valvoline synthetic simply because I sleep better knowing it's in there.

http://p083.ezboard.com/ffjr1300owne...icID=536.topic

 

That is a good read. I find synthetic too expensive to use in the cummins. My TDI VW comes with it and its is recommended for it, I think mostly for winter starting. It seems to make a big difference at -25c.
Bob

 

The diff between the price of synthetic and dino oil isn't to big of a sacrifice considering the cost of an overhaul. I want my engine to last as long as possible and synthetic will make it go farther.

I have a 92 Chevy S-10 blazer with almost 200,000 miles on it. I have run Mobil 1 in it since I got it and it doesn't pump any oil past the rings and compression is still good. The valve seals are always a problem but since I maybe lose a pint of oil between changes it isn't worrisome.

I only change it every 6 months also. If you can run synthetic oil twice as long between changes then your cost will probably be even overall.

Edwin

 

While I am a big fan of synthetics, I have to say that I have been VERY impressed with the amazing advancements in dino oil chemistry.

As dino oil gets better and better (at a relatively cheap price), my arguments for synthetic get weaker and weaker.

Check out the new CI-4 Rotella 10w30. Very impressive.