I've seen a lot of posts about diesels and oil pressure, but not much on gas engines. My 73 450sl used to idle at about 30, and otherwise run at the max 45. Now, after switching from regular 20-50 to 5-30 synthetic, it idles at about 25, but still goes to 45 otherwise. The engine has about 112,000 miles. Is the drop in idle pressure anything to be concerned about?

I am assuming that your numbers are in psi, am I correct?

If so, 25 psi at idle is othing to be concerned about. The drop in pressure has to do with the use of a lower viscosity oil.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

Sounds perfectly normal. My 4.5 idles at ~30psi warm and ~15 psi hot, with the needle pegged upon acceleration.

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.