Low Oil Pressure ?
 

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.

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.

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.

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.

FYI: Found cause of problem
 

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........

Re: FYI: Found cause of 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 ! ! !