Chrysler Repair: oil pressure decrease at higher rpm?, oil pressure gauge, voltage supply

Question
88 caravan 6 cyl When stopped in park the oil pressure gauge reads fine even when i bring the rpm up to 3500, but when driving when i reach 2000 rpm the oil pressure gauge will drop sometimes dropping to 0. Changed the filter and added new S.W.10  30 oil problem still there.When driving at 2000 rpm if i back off the gas the pressure goes back up, this happens all the time around 2000 rpm from start to 50 mph. I don't understand why it only happens when the van is in drive. Could it be the oil pump, oil pan or just the gauge?
Tks garth

Answer
PS: You might try adding a higher vicosity oil as you burn off the new oil, and then next time you change it use that weight. You could use 20W-40 or 20W-50 which will raise the oil pressure under the same operating conditons compared to 10W-30. Use the same type of oil as the new 10W-30 that you just put in, just increase the viscosity number. You probably have quite a few miles on the '88 engine so this is a possible 'fix' for a while.
Roland


Hi Garth,
That is a new one on me. I can only conjecture: could there be a difference in bearing clearance when you are actually powering the car vs. spinning it in neutral? Could there be a problem in the voltage supply to the gauges (do any of the other gauges change their position similarly)? Could you put a pressure gauge in place of the sender and thread it out from under the hood so you could read it while driving?
You might ask an engine rebuilding shop if there is some explanation that they would have? Please let me know if you get a plausible explanation.
Roland