last week my oil pressure gauge would bottom out when sitting at idle in gear, it would only do it after i drove awhile. The oil pump was just changed 3000 miles ago, i have already changed the sending unit out and that didnt help. What is my next step? Its a 98 4.6 with 164000 running 5w-30 with motorcraft filter. Forgot to mention it only drops all the way down when i put it under load at idle, ie turn the steering wheel other wise the gauge will just bounce around in the normal range. The gauge reads normal when in park

 

as long as its not knocking i would say its a gauge or you got a defective sending unit.