Mercedes-Benz W123 low oil pressure
What is the normal oil pressure of the W123?
The W123 gauge is mechanical, and its scale ends at about three bar. As a guideline, on a warm engine the pressure should be at least 0.3 bar at idle and 3 bar at 3000 rpm. The pressure often drops when warm at idle, and on old engines that is common.
Why is the W123's oil pressure low?
The most common cause is a clogged or wrong oil filter, and changing the filter often brings the pressure back up. Other causes are the pressure relief valve sticking open or its spring being broken. Also check the gauge's sensor: a cheap aftermarket sensor gives varying readings.
Is it a concern if the oil pressure rose after an oil change?
Usually not: high pressure is better than low. With new oil the pressure can be higher at first and drop gradually. A clogged filter can also raise the pressure, so make sure the filter is the correct one and properly fitted.