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OK, but QuakerState is barely a step above Pennzoil (yep - waaaay down there). IMHO, of course. /forums/images/graemlins/smile.gif
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I work with a guy that'll argue that statement, and can back it up.
He has a '93 cummins with 130K on it. He changes his oil every 10,000 miles, wether it needs it or not /forums/images/graemlins/smile.gif! Actually everyother oil change at 7,500 miles he pulls a sample and sends it too blackstone lab for analysis. Comes back OK and good for 10K. Could go longer but even 10K makes it easy to track when it needs to be done.
He is running longlife pennzoil 15w-40, buys it in 5 gallon pails and purolator filters. Only 1 filter per change also. Oil is darn near as clear coming out as when it went in. I run Mobil delvac 1300, 15w-40 because Meijer carries 2.5 Gallon jugs.
You can't get 10K change intervals from a 6.2/6.5 however. The oil gets dirty from the soot past the rings. That and the lower crankcase capacity.
I've seen his oil results and dang I hope mine runs like his!