I read somewhere here that replacing the O-rings at the bottom of the oil filter center tube might reduce or eliminate hydraulic lifters in my 87 300 D.
After a road trip today from Rhode Island down to New York and back my lifters were louder than usual. This afternoon I pulled the center tube and the two O-rings were worn and hard as a rock! I put some new O-rings in and the oil guage does not go below 2 bar.at 650 rpm idle! Normally it at idle the guage showed 1.5 bar. Now the engine has not even the slightest valve tap and I was going to replace lifters! Guess I dont need to now! Thanks to whoever posted about replacing O-rings.