I am the original owner of a 1991 350 SDL with 159K miles on it now. I had my oil changed recently at my local MB dealer as I have done many times in the past. The engine has no history of oil pressure, or any other significant problems.

When I picked up the car after the oil change I noticed the oil pressure gauge twitching a little bit at idle, I have never noticed this before. Today after about 350 miles the pressure dropped to near zero at idle and "2+" on the gauge at 2300 RPM and above. It was always pegged at "3" at anything much more than idle in the past. I believe the gauge because I can hear some lifter noise at idle that has never been there before.

I am very interested in opinions on what might be going on here?

Thank you.