on most cars the Oil pressure gage reads in PSI with some accuracy, on MBs you get Zero to Three. Mine pegs at three when rolling down the road and hovers around two when warmed up at idle. is there any value assigned to the numbers or is just a little better than an idiot light? is it roughly kPa?

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1993 MB 300D 245K died.

It reads in BAR. 2 at idling and 3 when off idle is perfect. 1 BAR is equal to 14.5 PSI

Some light reading if you're curious:
http://en.wikipedia.org/wiki/Bar_%28unit%29

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2004 F150 4.6L -My Daily
2007 Volvo XC70 -Wife's Daily
1998 Ford F150 -Rear ended
1989 J-spec 420SEL -passed onto its new keeper
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold

makes sense 1 BAR = 100 kPa = 14.5 PSI

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1993 MB 300D 245K died.

Gotta love the metric system, it's all related to real world stuff, not arbitrary like the US system

1 kg = cube of water 100 mm by 100 mm by 100 mm = 1 liter

0 C = water freezes 100 C = water boils at sea level

1 bar = normal atmospheric pressure at sea level

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

The gauge us not terribly accurate, unfortunately, and tops out at 3 bar or ~45 psi while the oil pressure typically exceeds 3 bar when the engine is above ~1000 RPM. The factory notes that apparently low oil pressure at hot idle is not a sign of trouble so long as the pressure rises as soon as the engine is above idle.

I have a separate mechanical oil pressure gauge on my '95 E300D; it registers over 60 PSI (~4 bar) when the engine is cold and first started. Hot idle is between 15 and 20 psi or just over 1 bar. The factory gauge shows closer to 2 bar at hot idle so there's a significant error.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

This is ona OM617.952
The actual Oil Pressure on My Car can go up to 97 psi; about 6.69 bar.

The Pressure Relief Valve in the Oil Pump opens and 110 psi; about 7.58 bar. So that would be the most pressure you could get out of the Oil Pump.

At a Hot Idle I get 1.5 bar; about 21.75 psi but the hot idle pressure is still consided OK at I believe it was 0.3 bar; about 4.35 psi.
Your, gauge will not accurately read 0.3 bar.

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84 300D, 82 Volvo 244Gl Diesel