I've done some more work on the factory oil pressure gauge install experiment and I'm less enthusiastic about it now. Until I actually took the gauge out of the cluster to examine it I couldn't tell that it is a simple bi-metal type of gauge design. Here is how it works and you’ll soon see that it is very slow to react to changes in oil pressure.

This type of gauge operates by heating a small coil of Nicrome wire (or similar resistance wire) that is wrapped around a thin strip of bi-metal material. That thin strip of material flexes as it gets hot, thus driving the needle through a simple gear mechanism. The more current that flows through the Nicrome, wire the higher the needle moves.

The oil pressure sending unit (mounted on the motor block) is a mechanical potentiometer that converts a rising and falling pressure reading into an inverted resistance reading. As the pressure goes up, the resistance goes down. Therefore, as the oil pressure rises the resistance goes down, the current through the Nicrome wire coil increases and the needle moves higher.

This type of gauge is slow by design. It may take as long as 15-20 seconds for the needle to show the correct pressure as the bi-metal strip has to have time to heat up and cool down.

In my opinion, any oil pressure reading is better than an idiot light but the slow reaction time of the factory gauge may not be what many of you are looking for. I will probably go ahead and install the gauge since I have it in place but I may eventually add an aftermarket gauge elsewhere.