I realize this is an issue that has been debated again and again...and just when you all had me pretty much locked in to an opinion on when to change oil [yes, I do very much respect the things you all have to say], I stumbled across a European website that contained the following (yes, I understand about UOAs)...One of the authors of an article on oil change intervals had this to say..."I am an engineer for a big OEM and I feel that for best engine life, if you drive the car hard or in a short hop driving cycle, you should change the oil [using synthetic] every 3000 miles." He goes on to say that the extended intervals in Europe are the result of pressure on OEMs to reduce the cost of ownership and to "green up" their business. He goes on to say flat out that "In my own oil testing dino oil breaks down and loses its viscosity after about 1500 miles which is manifested by loss of hot idle oil pressure" and that Motul and Mobil 1 are good for 3000 miles before breakdown occurs. (The only oils mentioned at the site are Mobil 1, Motul and Castrol Formula SLX [0W-30]. He goes on to cite that he has dissembled many engines and the difference BTW 3000 mile and 7-8000 mile intervals "is night and day." "The longer interval car will have a layer of sludge on all surfaces. The 3000 mile car will have only a brownish discoloration to the parts. Another author says that he EXPECTS 180,000 - 200,000 miles out of engine and transmission and that this is the way to get it (he didn't talk about changing tranny fluid. There is a lot of other good stuff including a very detailed breakdown of driving style, ambient temperatures and the intervals that should be used. While I see some holes in the arguments made, overall this website made some compelling points. I offer this not so much to reignite debate but to let you all have some info to include in your grey computers, although I wonder how well a chain of UOAs for an engine and an actual teardown of the same engine correlate.
Regards...
Regards...