I am interested in the possibility of changing over to Schaeffer 7000 5W-30 in my passenger car. Does anyone have any long term experience with this oil after long term usage, say 50,000+ miles? I'm interested in knowing if any mechanically adapt people out there (not me, that's for sure) saw clean engines with Schaffer after many miles. Or does is gunk up in the long term. Just ask'n. Thanks.