myredracer wrote:
Changed the oil & filter yearly, had about 140K miles on it and it always ran great. The oil pressure was good right up to the end (unless that gauge was defective).
Understand that a Ford truck oil pressure gauge is not really indicating pressure. It is operated by a on/off pressure switch and has a resistor in the circuit on the back of the gauge to hold the gauge in the position you saw it in. If you think it fluctuated it was due to variances in system voltage. My '91 Ranger has the same thing, and it has been done this way since some time in the '70's or '80's right up to the present on all Ford trucks. You may have only had enough pressure to make the switch make contact (10 psi or so) and no more. Google Ford truck oil pressure gauge for more info, and ways to jumper the resistor and add a real pressure transmitter to the engine.
Charles