I had installed a Summit oil filled gauge. It worked when cold but went to 0 when the engine compartment heated up. Calle Summit Tech and they said none of them work when hot. Sent it back. Did a little research on Amazon looking for one that works. and Mr. Gasket said to ice it down when hot to get a good reading. Some others say they have a vent on the guage and you need to vent the guage when hot to get a reading. Any suggestions on one that works? I have my old  vaccum/fuel pressure guage hooked up temporarly  and it works but is not a permanent solution. The guage is mounted on the frame where the fuel line ends up on my T Bird,