FYI, the oil life reading is based on engine RPM and temp if memory serves me correctly - its in the manual. This is a poor gauge of engine oil life, the best gauge is oil viscosity. GM and others have been working on a true oil viscosity sensor for several years but to my knowledge has not deployed it. Oil viscosity changes as the oil breaksdown under use and is also a good indicator of other contaminants entering the oil stream such as metals. I'd guess that one of their difficulties is in a calibration scheme that works for the myriad of oil choices/brands.
In absense of a true first order sensor of oil life (such as viscosity) I'm sticking with the every 3000 mile rule of thumb - too bad, because I'm sure there are plenty of times when our vehicle's oil doesn't need to be changed as often.
JJ
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