[Otto]

If the oil pressure measured with the guage is correct, then you should look at the idiot light switch or the circuitry associated with the switch. If you know how to use an ohm meter, disconnect the wire off the back of the idiot light bulb and measure the resistance(OHMS) in the wire between the light bulb and the connection on the idiot light sender in the engine compartment. Old wires gain resistance with temperature increase, a common problem we have noticed over the years. If the resistance in the wire that goes between the bulb and the sender is greater than zero, then that is the problem. If the resistance is zero, then you must have one of those elusive homotrons in your car.