oil pressure
 

when I am driving I noticed my oil pressure isn't where it used to be. while driving at 40+ mph I'm only at 2 and a half bars instead of 3. when I press the brake to come to a stop the gauge drops rapidly to 0. on acceleration it won't hit 2 and a half bars until I'm well above 40 mph. Suggestions?

This is usually just a result of OEM gauges losing accuracy over the years. Oil-pumps rarely fail. If you've started to notice a clattering or ticking sound coming from the top of your motor then you know you're having an oil starvation problem.

Just to be on the safe side i would have the Oil Pressure checked by a new gauge either from a garage (this is a common procedure) or just replace the oil sending unit with an aftermarket piece from your local parts store.


Also, make sure that your oil dipstick is firmly seated in the tube, and check for loose hoses around the valve cover. Have you changed your oil filter lately? Switched brands of oil filter or different weights of Oil? If the engine doesn't have proper Positive Crank Ventilation PCV then you will see a drop in oil pressure. Also depending on vehicle mileage the clearances between those bearings are growing and sometimes a thicker weight of oil can help cushion the aging bearing clearance issues.

no ticking noise noted. it is just a recent issue. I did notice slight oil leakage around the oil cap and under by three oil pan, but this is nothing new either, maybe the slight trace of oil by the oil cap, but nothing else. I changed the oil filter in september, I use bosch premium brand. I also am running 20-50.....I usually run the heavier weight because my car is usually running at 80°C + the oil dip stick is not really snug, but it isn't overly loose either

Check to make sure that oil cap isn't dis-lodged or improperly seated, it might even be the rubber gasket under the cap going bad allowing too much pressure to escape through your oil fill orifice. One way to check would be to have someone sit in the vehicle while its running, and you unscrew and screw the cap back on to check for any changes in pressure and or rise in engine idle. If possible remove the cap all together and place your hand over the oil fill orifice to plug it then see if oil pressure rises.

oil cap gasket was replaced in July, but I was never really thrilled about it because I did notice that I had slight traces of oil around the oil cap after, but the parties was fine so it wasnt broken so I let it be. I wonder if I should just replace the entire oil cap to be safe and see what happens

For sure, thats essentially a massive vacuum leak, as well as a nice gap for moisture and crud and dust to enter your lubrication system. If you just got a generic oil cap i'd try to find a model specific preferably MB cap for sure.