I've noticed that my '92 BMW 535 has a problem with low oil pressure when parked at an incline. I made two runs getting sand today, and to get the trailer in the right position I had to park the car in the steep area of the driveway. Both times the oil pressure light was on when I started the car, and the second time it even came on as I was backing in. I tried restarting the engine, but same thing. It wasn't until I got the car up on level ground and restarted the engine the light finally went out. Mind you, both times I had to drive up onto the street, reving the engine and with the trailer behind, without oil pressure. Obviously, that can't be good. Is this a design flaw in the engine, or is there something wrong with my car? I checked to oil level afterwards and it was perfect, right below max. I've never had any problems with low oil pressure before.
As you can see in this picture, it isn't even that steep:
Ulf