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  1. '06LBZ Used Oil Analysis: high copper?

    06-07 LBZ & LLY Duramax Powertrain
    Truck now has 55,000 miles on it. I've been using Amsoil synthetic 15/40 for over 30,000 miles with no problems, changing the oil and filters at about 10k intervals. I run slightly extended oil change intervals based on UOA testing (by Blackstone) at 5k mile intervals, usually at least once...