I have 79 f150 4x4 big block 400 4 speed, as engine gets warm oil pressure goes down, according to the gauge. When the engine first starts the needle on tha gauge is at least half way in the normal range, after it warms it has almost bottomed out at the low side of the normal range on the gauge. There is no difference in how the engine runs whether it is showing high or low. It runs flawlessly, no engine noise at all and doesn't use any oil. Could the oil pressure sender be bad? I just changed the oil and that made no difference. Any one have any suggestions on what could be causing this or is it just the gauge?

 

you could try a manual oil guage.

 

Inspect the wire where it plugs onto the sender, they were know to break inside the insulation. If the molded end (that connects to the sender) is real floppy the conductor could be broken. If all seems well then replace the sender. Taking a direct pressure reading is advisable but requires a gauge that most people don't have.

 

changed sender all is well