Low Oil Pressure 79 450SEL?
 

Does anyone know if it is abnormal for the oil pressure to drop to 5-10 psi when engine is idling and hot (first line on pressure gauge is 15). I suspect the oil pump is worn, but before spending the $300 to replace it, I was hoping for some insight. I know that some reduced pressure when idling is normal. When I speed up the engine, the pressure does not build all the way up to the peg at 45 psi until I get to about 2000 rpm. Even when I am driving, at betweem 35 and 40 mph in top gear the oil pressure is only about 30 psi (below 2000 rpm). At all other speeds it is up to 45 at least. I have driven lots of Benzes and I have never seen this before, so I think there is a problem. Using 15W50 Mobil 1.

forgot to mention -
 

car has 130k miles

Sounds like it is still within spec, .7 bar as an acceptable low oil pressure. It should peg out a little earlier though.

Have you checked the pressure with a different gauge? Maybe the gauge is failing. When was the last oil change?

Check out the little stuff first.