Tru2Chevy Posted November 29, 2005 Report Share Posted November 29, 2005 10-30 or 10-40 Mobil1, depending on the season. - Justin Quote Link to comment Share on other sites More sharing options...
cutlass1991 Posted November 29, 2005 Report Share Posted November 29, 2005 Castrol GTX Quote Link to comment Share on other sites More sharing options...
pitzel Posted November 30, 2005 Report Share Posted November 30, 2005 A cab company I am familiar with runs the GM 3.1L V6 out to approximately 40k miles on a single oil change with a good synthetic. He uses Used Oil Analysis, and has experienced no detectable excessive wear or sludge contamination resulting from the use of a long interval. My 3.1 manual recommends filter changes every 15k miles. Even with a synthetic running for long drains, there isn't any reason to change the filter prematurely. If one's in Canada, Imperial Oil/Esso/ExxonMobil XD-3 Extra 0W-30 is very excellent stuff for the 3.1's, and dirt cheap too for a full syn. Quote Link to comment Share on other sites More sharing options...
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