oil gauge

Check the gauges. If you can't figure out what is wrong, ask a friend, then take it to a mechanic as a last resort.

I have seen a lot of the 4.0's spin cam bearings the oil pressure will be good on start up but consistently drop as the engine warms. It will have low oil pressure with the light on at idle but seem to have normal oil pressure when you rev it up. The only way to check it is to screw a manual gauge in where the oil pressure sending unit goes and see what the actual reading is.