Where is my oil going? Part II

Ok, I will try to word this very clearly. Just went down to my car which has sat overnight on perfectly level ground. Turning the key to "On" position but not running the electronic gauge reads right in the middle, first 4 segments from the top were empty or not lit up, the other 4 were illuminated. Waiting for the 5 second countdown to finish I started the engine and almost immediately oil pressure went to 4.75 or 4 3/4 at high idle. It did not go higher bringing RPM's up to 3K. After idle automatically kicked down to 650 RPM's pressure still at 4.75. After fully warmed up oil pressure dropped to exactly 2 bar, when RPM's were brought up to 3,000 - 4,000+ oil pressure went right back to 4.75 bar. Let off gas and pressure right back to 2 bar. What is the electronic gauge telling me being half lit up? Thanks everyone for participating in this.

The bars are showing how much oil is in there and is very accurate. I wait as per the manual until all the bars a gone and the last one is flashing. I then drive past the dealer and they top it off. No charge. When I had the RMS I would go through a quart <750 miles. With the replacement engine i put a quart in at about 2500 miles. That was with one auto cross and three DEs.

Your oil level indicator shows how much oil is in your crankcase it has almost nothing to do with your oil pressure guage. I say almost because you would have to be down probably 6 quarts or more before you would see a drop in oil pressure especially at idle. Remember this car has over 9 quarts of oil when full. A big Chevy V8 only has 5 1/2.

If your pressue gauge does not show a lower than normal reading when you are down a quart of oil on a warm engine....get a new sending unit. The amount of oil in the engine IS directly related to and directly effects oil pressure.

So if I understand correctly then, having only 4 segments lit up on my electronic gauge means I am a quart low ? Thanks everyone for help and input, I hope this clears up some questions for many.

1999Porsche911 I disagree with your statement about the relationship between oil level and oil pressure although I am also willing to admit I am no expert and I am willing to be schooled on this. It is my opinion that oil pressure is determined by the viscous resistance offered by the bearing clearance against the output of the pump up to the point of the oil pressure relief blowoff. When the oil pressure drops it is usually as a result of viscosity drop over temperature. When oil levels fall to the point where they manifest lower oil presssures you are starving the pickup or you have aerated feed due to cavitation, a very dangerous condition in a highly stressed engine. Again I'm not looking to argue but I would like to understand your reasoning. Thanks, Bob

I agree with Webtool but hey what do I know. It seems to me for the amount of oil to affect the pressure output of a gear type oil pump it would have to change the input pressure to the pump which it could only do by developing a head of pressure from it's height above the pump. How high could it get in a flat boxer type engine? So I just don't understand. The pressure always falls as the engine warms up but that is due to the decreased viscosity of the hot oil.

Cavitation also results in lower oil pressure since air compress's & fluid doesn't. If your crankcase was pressurized, your dipstick would blow out.