My '01 ,auto., sounds like it has piston slap when the engine is cold. It's ok at ldle but pulling up a hill or moderate throttle and I hear a tapping noise. Sounds like an old lifter when they were loose. As the engine warms it fades away. It's got 21k and I've used Mobil 1 since the second oil change. As you would expect, the dealer says it's fine. I should add that my dealer's Service Dept. is.... uh...USELESS. I'll save that for another thread.