Synthetic rocks. Let's put it this way, after 80,000 miles each on Mobil1 full synthetic post-breakin, both the 1994 Z28 and 1997 Suburban keep the oil clean for quite some time (5000 mile oilchanges) into their changes. 10w30 in the Suburban, and 20w50 in the Camaro (LT1s don't build enough pressure with 10w30 synthetic!).
Whenever I get a new engine in my truck, it'll go synthetic too.
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Project 1970 - soon to be seen at
http://milhouse.treylis.org:81/