The car: BMW '90 E30 320i Cabrio with the six-cylinder M20 engine.
The problem: the red engine oil warning light inside the instrument cluster (not the check control) lights up after some driving. But the engine sounds and works just fine. Turning off the engine and restarting causes the light to go off. But it comes again after some cruising. I cannot say for sure but it seems like this happens rather on hot days.
I had the engine oil changed about 6 weeks ago but to be honest I didn't pay enough attention and I'm not sure which grade the mechanic put in. The problem with the warning light started about two weeks ago.
The BMW is a weekend driver and does not get moved daily.
What could be the most likely cause for this problem? Oil pressure sensor? Motor oil too thin? Something more serious?