RootMachine

95 90 12v v6

Changed oil, no signs of leaks, not eating oil, oil level always normal, engine is running normal, no ticking, sounds/drives like it should.

When I first start my car (when cold) the oil pressure stays ~2.3 bars and when driving ~2.5. Once the car warms up to full temp the pressure will drop to just below 2 bar while driving. When at idle, it will drop almost past 1 bar, and flick on the oil light. If I rev it up just 200rpm from idle the oil light will turn off.

Could this be a result of my pump going bad? Sensor? Why does it happen when warm? Any ideas?

moribundman

How many bar pressure at 3k RPM and operating temperature? Should be 3-5 bar.

What sauce are you using?

SiV6Qcoupe

Had the same drop in oil pressure happen on my V6 when the no.1 main bearing spun dry due to the oil pump failing to prime on startup. If this problem occured after an oil change it's possible that the pump had air trapped inside and was unable to suck oil up in time to lubricate the bearings. A drop in pressure like that will nearly always be wear to the main bearings :-( especially if the oil warnings are in unison with the oil pressure gauge!

If the drop in pressure was a gradual decrease I would suspect wear to the pump and occasionally on startup the pump will not prime and your gauge pressure will read 0 bar and the audible warning will occur.

RootMachine

audible warnings yet.. Maybe ill try a new sensor, if its not that my guess is the pump

RootMachine

At 3k rpm its at or just over 2bar...

I'm running Valvoline full Synthetic 20w-50

moribundman

indicates overly worn crank bearings. 20W-50 is a little extreme. Have you always been using that? Where are you located? I'm asking because of ambient temps.

RootMachine

I ran 5-40 during the winter monthes and just recently switched to 20-40.. The reason i switched was because a local shop runs that in the audis they service. I live in washington btw.

Does the pressure drop when warm because the oil thins out (vicosity?) when heated up?

moribundman

Oil pressure is nothing but the resistance oil channels, oil filter, and check valves present to oil flow. The bearings themselves "draw" in oil as long as fresh oil is supplied. The oil film that keeps the bearing parts seperated does not depend on oil being forced into the bearings.

Oil pressure rises with viscosity and RPM. Low oil pressure can indicate worn bearings.

Don't trust your oil pressure gauge. Have the oil pressure and lubrication system checked by a competent mechanic.

I think 20W-50 is too viscous. It won't hurt the engine, but it robs power, it does make the oil pump labor harder, it cools less, it doesn't aid the lowest possible startup wear, and it will affect fuel economy somewhat negatively.

5W-40 is most likely the best all-year-round viscosity you can use.

RootMachine

thanks for your help man, much appreciated!

Ill be visiting our local shop tomorrow, ill post up what we find.

moribundman

Good luck and let us know!