I would like to add an oil pressure switch (*not* sensor) to my 1985 300D.

The oil pressure specification per the FSM is no less than 3 bar (gauge) / 43.5 psi (switch) at operating temperature idle.

Of course, one can spend an eternity online looking at the almost limitless number of oil pressure switches available for the world's vehicles. The trouble is this: With the rare exception, the psi rating is not provided because few people care what it is. They just want to make sure that they select the replacement switch that fits their car.

So, my inquiry:
How to find out the psi rating of a given oil pressure switch? If I show up at a run of the mill auto parts store asking for a generic oil pressure switch rated 45 psi, could they know? How else might I either find this information or find a source online? And I assure you, I've looked a lot recently.

Thanks for any guidance on this-

AM3242 is an AutoMeter 30 PSI switch. Searched on "30PSI Oil Pressure Switch". Try searching on the specific pressure you'd like.

Dwyer series A6 switches come in ranges up to 150 PSI and are adjustable.

Where will you port it in?

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Which switch used would depend on your goal. 1-2 bar is common at hot idle. Should be 3 bar all day long off idle. Also know the maximum pressure the switch can handle so it doesn't fail.

I've always preferred a gauge over a light but would strongly prefer both.

The switch could be threaded into the oil fill cap.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Direct quote from the 617.95 Engine Manual:

"At operating pressure, the oil pressure at idle should not drop below 0.3 bar gage pressure.

During acceleration, the oil pressure should rise again immediately and should attain at least 3 bar gage pressure at 3000/min."

It is also worth noting that the oil pump pressure is relieved at 7 bar, well above the range of the oil pressure gauge.

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My mistake. Thank you for the correction.

Have a look again at the spec. MB engines typically call out a minimum hot idle pressure of .3-.5 bar. Notice the decimal point!
Engines in good condition will idle hot slightly above 1 bar, and even a poor engine will reach 3 bar before 3000RPM.

I sincerely hope that you never suffer the sort of eye damage that has befallen me and made decimal points and far more important things in life difficult to see without a great deal of effort.
Good luck to you.

VW put a 1.0 bar (15 psi) oil pressure switch in their TDI engines. I adapted one for my ‘95 E300D. If the oil pressure drops below 1 bar, which it should never do, the switch operates a very bright flashing red LED in the instrument cluster. In operation, the LED occasionally blinks once or twice when the engine is hot and returning to idle, before the EDS system gets control and brings the idle up to normal. This warning should allow me to shut down the engine before it is damaged.

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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
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"Oh lord won't you buy me a Mercedes Benz."
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