I have a 1993 300E 4Matic, and was wondering if the oil pressure readings at highway speed is normal. At 3000 rpm's, in a warm engine, my dashboard gauge is reading about 2.5 bar, and it never goes higher than that. I recently changed the oil and filter (10W30), and put in a new oil pressure sending unit.

The oil pressure goes quickly up to 2.5 from idle, but not sure if 2.5 bar is a concern.. thanks....doug

What is your reading at idle (600-800 rpm)? Maybe someone replaced the needle on the gauge and did not install it back properly. It is an easy mistake which can make you wonder? I don't know how to check the oil pressure on the engine? Maybe with compression test? I believe your reading at 3K rpm should definitely be at 3 Bar.

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1984 MB 300D Turbo Diesel W123 Sedan 132K
1987 MB 300D Turbo W124 Sedan 295K
1983 Porsche 944 104K
1989 Audi 80 Quattro 180K
2002 Audi A6 3.0 Quattro Avant 49K (Wife's car with warranty )

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A compression test will not help in your case. it has nothing to do with oil pressure.
a) What,s the mileage on the car?
A check with a handheld pressure gauge would give you a better indication if there is a problem or not.
2.5 bar is a bit on the low side as it normally goes up to 3 at your indicated RPM.
What is the pressure reading at idle.?
jackD

The mileage on the car is 130,000 miles. The oil pressure reading at idle (when warm) is around 1 bar. The engine does have hydraulic lash adjusters, and have never heard any rattling from them upon start up.....

I think your engine is fine as low as 0.3 or 0.5 bar at idle. It should peg at 3 above idle.

Part of the problem could be the oil. I don't think any -30 oil is approved for modern MB engines above 10C/50F. xxW-40 and xxW-50 only. Or maybe it's that cold where you are.

It could be a problem with the gauge. Have a shop temporarily hook up a mechanical oil pressure gauge.

Sixto
91 300SE
87 300SDL
83 300SD

I recently had the same problem in a customer's '89 300E. Since it was due for an oil change, we did it and then the pressure returned to normal. I am led to believe a blocked filter may have contributed to this.

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Regards,
Aaron

Doug, you can check your oil gauge. Disconnect the wire from pressure switch - gauge at 3. Ground this wire - gauge at 0. All with ignition ON.

I am going to have to say that you have to use thicker oil. According to the temp/viscosity chart that I have a -30 weight oil is not approved by Mercedes to be used at any temperature.

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Ali Al-Chalabi

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

I was tempted to say what Ali said but my 91 300SE manual says 10W-30 and 5W-30 are okay below 50F. Balance that with recently published MB approved lubricants list which show no -30 motor oils.

Sixto
91 300SE
87 300SDL
83 300SD

my manual also says 10W30 is fine at this temperature (it is a balmy 25 degrees outside), but I will do an oil change today using 10W40 to see if anything changes, at least to eliminate one variable....

For ever and ever MB has had only 1 Oil Pressure Specification . . .

At OPERATING TEMP the gauge must be at FULL SCALE@3000RPM

That's all folks . . .

I am just curious, how could you not install the needle correctly? if it sweeps up and down is there a chance the needle not installed all the way or something? I am asking because I have some needle issues and wanted to see how could that be a reason for concern. Thanks.

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Joe95E420

For your info, I found the source of the low oil pressure. I had changed from 10W30 to 10W40, and saw absolutely no difference in pressure. I then changed to a new oil filter. I didn't think changing to a new filter would make a difference since the current filter was only 3 weeks old.

The new filter solved the problem. Apparently, the 3-week old filter must have been defective, maybe a overly strong check valve.. Nice to have a $8 fix to the problem........

BETTER SAVE THAT OLD FILTER AND RECEIPT for the OIL and FILTER and record the DATE and MILEAGE you installed it.

There's a chance that you may have lower end damage and that if the CORRECT filter was installed, the manufacturer may very well be liable for damage ! ! !