Ive been changing my oil since i got my truck 30,000 miles ago and have been using the same oil and oil treatment also. Prior to today change the oil was usually about 40 psi i think but today after my oil change i noticed that it was staying around 65 - 70ish psi. while watching it i noticed it drop all of the sudden for no aparent reason from 70 to 40 in like 2 seconds. throughout the day ive gone out to start my truck and drive around a bit and its done the same thing each time. itll start around 65 70 and after some running time just drop to 40 and as low as 35ish. anyone have anything to say about this. what should my pressure be at idle?

used royal purple 10w-30 4 quarts and a bottle of lucas oil treatment. fram filter. put seafoam in my oil about 80 miles before the change.

 

Could be a bad oil sending unit or a piece of debris somehow causing it.

 

i was considering replacing the sending unit if the problem persists. what pressure does yours run at.

 

Your problem could be the Lucas. Stop using that ****.

Also, why are you using the highest quality oil with the lowest quality oil filter?? Fram filters are the worst in the business. Use a Purolator, WIX, Napa Gold, Motorcraft, Mopar, Mobil 1, or a Baldwin.
http://minimopar.knizefamily.net/oil...reference.html

 

Mine runs right at or slightly above 40 psi.

 

i sit at about 40 until i tow something heavy, then i run about 35, until the oil cools some

 

mines just a hair over 40 also. i agree with purpl, fram is crap and you shouldn't need the oil treatment since you've been using it for so long. the seafoam could have worked some sludge or debris loose and it caked your sending unit up or clogged the pump a little.

i have a similar issue with my camaro, i changed my sending unit a while back because the pressure went off the gauge. after the change it goes just under max pressure (80) till it gets hot then it hovers around 65ish when the rpms are up and 30 at idle. the guy at the parts store said it could be a stuck valve in the pump.
so i'm curious to find the answer to this question so i can get that camaro figured out.

 

Fram filters are junk. I'd start there.

 

Sounds like the pressure is "hanging" going from a drive to idle status. I'd first replace the filter (cheapest "fix' first) as the bypass valve may be faulty, then suspect the oil pressure sending unit.

The oil pump is driven by the oil pump drive shaft connected to the distributor and driven by the rotation of the camshaft. The higher the RPMs, the higher the pressure. The bypass valve in the oil filter is supposed to dump some of the pressure at higher RPMs, but it sounds like the valve isn't working quite right.

There will be a little delay in the oil pressure drop, but it shouldn't be excessive.

 

I agree start by changing oil filter...
might top off level with a quart of 'risoline" that would address any sludge


lucas is good but not for routine -

use for those dog days of summer stuck in 1000deg beach traffic or a low press hi milage situtation.