I'm running a 91 Ford 5.0 in a 2001 NB Miata and my oil pressure gauge reads incorrect. With the engine off the gauge reads at the 12 o'clock position and after starting the engine as the pressure increase (measured with a mechanical gauge) the instrument gauge goes down. I read in an old build post of the same problem and the response was that the oil pressure sensor was the incorrect sensor but there was no mention of what the correct sensor should be. My Miata had the oil pressure switch with the gauge that read a constant oil pressure no matter the engine RPM. Is there a way to use my gauge and get a correct representative reading? My gauge doesn't have any numbers on it just a few marks showing a percent of full scale.

 

This might help you. Miata Community Wiki | Turning the NB Oil Pressure gauge into a real gauge There are a few other articles pertaining to this matter in their GARAGE section as well.

 

Thanks this works very well.