I put 191,000 on a 97 saab 900 turbo without any oil-related problems using mostly M1 5w30 and 10W30. I always did 3-5k mile change intervals and did a chemtool flush every so often. It never missed a lick, never leaked, never burned a drop between changes and was spotless under the valve cover. Was it overkill? Maybe, but like I said, 191,000 miles w/o a problem. If she weren't in a 3 car pile up I'd still be behind the wheel....