Erratic Oil Press. Indication

[knob]

I have a 92 Explorer Sport 4.0 w/ 172,000 miles that runs great. When driving normally down the road, the indicated oil pressure will fluctuate wildly from 0 to middle of the gage, water temp shows normal. I suspect the oilpressure sending unit is bad, but it may be the actual oil pressure is low. Any suggestions on what to check to see what is causing these indications?

 

[JDraper]

I'd suggest pulling the sending unit out of the motor and plugging in a real pressure gauge. The factory gauge is not truly a gauge, but more of an idiot light with a needle. IIRC, it only has either 2 or 3 positions-no pressure, good pressure and high pressure (not sure on the last one).

 

[unclemeat]

Do it soon, when mine did that it was the oil pump failing.