My oil light comes on only at high RPMs, and goes off when I return to idle--even though the dipstick shows the level is correct. Here are the symptoms:
1) The car is a 1986 560SEC with 185,000 miles
2) The oil pressure is correct at all RPMs
3) There is no sign of blow-by
4) Compression test shows all cylinders > 90% of spec.
5) The oil level is always correct when I check the dipstick and there are no signs of significant oil consumption over time.

It seems unlikely a faulty sensor would show a consistant dependance on RPMs. Could this be from plugged return channels? In other words, the oil is being sent faster than it is returning, resulting in a low average level? Any other ideas? Thanks for the help guys! Andrew Seidel.

Too much oil causing the oil to foam would be my guess. Also light weight oil will contribute to problem. Try removing 1/2 to 1 qt.& see what happens.

Thank you for the idea! I am using 20W-50 and will remove some tonight.

My 190 2.6 has a similiar quirk. After about 45 minutes of driving, the low oil light comes on and stays on until I stop and turn off the engine. If I imediately restart it, the light is off and only comes on again after another long drive. Oil levels are fine when checked. I suspect blocked returns which a cleansing flush could resolve, what do you think?

That is what I was thinking, however, most people think the oil is foaming. One reason I have not tried a flush is that some of the gunk is holding the engine together!--not sure how to unclog only the return path, except to wait for rebuild time.

I would suspect an electrical problem more than an oil problem. If your oil light comes on at high rpm and it is correct your engine will be toast in no time.

While I wouldn't believe that your engine is that delicate to be bonded with the gunk, you could pull the valve cover and scrape the top. Another way to check for this problem is to check your level immediately after getting the signal. If it is low then and not later after settling, It could be all up top. This usually leads to oil seepage from the valve cover gasket, which I have not experienced.... yet.

I found that the nuts on the left valve cover were loose and there was slight seepage around the gasket. However, if the oil was flowing normally, it probably would not leak through the gasket, even if the cover was loose? I will test as suggested and see what effect tightening down the cover has had.