You could be many miles from home with lots of lumps of engine all over the floor and nothing of any value at all under the bonnet.

The oil pressure warning lamp is probably the most critical warning lamp on your dash. It warns you of imminent wallet raping and pillaging if you do not stop the engine IMMEDIATELY it lights up when the engine is running. It should go out when you start the car and not come back on again untill the engine stops AT ALL. It is a mechanical pressure switch which is pressed by the oil inside the engine which is under pressure. Should this pressure drop then the light comes on to tell you that there is no oil going round your engine to lubricate it. Either you have oil pressure problems or your wiring to the switch is touching to earth slightly.

DO NOT assume it is touching to earth slightly as if you do and it is in fact an oil pressure fault then your engine will become scrap metal pretty quickly! Check the pressure first and if it is ok, then move onto the wiring/switch.

It has NOTHING to do with the set up of the car.