Originally posted by psfred
Mobil 1 will have lower viscosity at low temps, higher at high temps, than dino oil, so I suspect you have crud in the oil passages, along with some wear in the adjusters. The thicker dino oil masks the wear in the tappets at low engine temps.
If it bothers you, stay with the dino. If you want to change, you will need to run the Mobil 1 for about 1000 miles, then change it and the oil filter, the filter and oil will be full of crud that has dissolved.
The lifter noise may go away with extended use of Mobil 1.
I would agree. I seriously doubt Mobil-1 is causing your noise problem. Much more likely to unmask an existing problem.
I switched to Mobil-1 at 80,000 miles with no problems whatsoever. And no, 15W-50 isn't "too thick."
What's your oil pressure? The other possibility is the well-known oil tube problem in the M119 engine which presents as noise in the valve train and lower than usual oil pressure.