Hey Guys,

I finally got a mechanical oil pressure gauge and I noticed this problem with my oil pressure fluctuating all over the place and having poor oil pressure when warmed up.

When starting from cold, the oil pressure goes up to about 50 psi and holds that for a minute or two, then drops down and starts fluctuating from about 20 to 40 psi as shown in the video:


Once fully warmed up, I am only holding about 7-8 psi at idle and 20 psi cruising around 2000 rpm or so. I currently am running 10w40 with about a half a quart of Lucas Oil Stabilizer in it. The Lucas oil helped the oil pressure (and, surprisingly, helped the leaking rear main seal), as before idle pressure was almost non-existent. Engine is a 302 of questionable origin.

 

The numbers that you quote are not at all alarming for a tired old 302.
Idle speed should be around 600.
Aftermarket gauges have a much shorter time constant than heavily damped stock gauges. Hence more rapid fluctuations.
Straight 30w oil will work just fine unless you are in a very cold area.

 

I had a Jeep that oil pressure dipped a lot once warmed up and it was determined it was rod bearings. Now, I am no engine expert, so don't go tearing into it on account of that statement. I was told that oil pressure at idle really only needs to be about 7psi, so it was plenty. If you have the leaky main seal and such, though, you might want to start a cookie jar savings account to freshen up the engine sometime before too long.

 

If you had your foot on the gas pedal any and the oil gauge PSI was fluctuating then, I think if the lower end has no knocking or other noises, I'd pull the pan can the oil pump pick up screen. If clear then I'd replaced the oil pump.

But first put in heavier oil or add a can of STP an see if still is fluctuating.
Orich

 

A can of seafoam, or any other de-gunker/engine flush may help clean out all the passages and get the flow going again.

If your going to replace the oil pump, install a high volume pump.

 

Meling high volume pump, will give you more oil. The high pressure pump will give more pressure. As oil heats up the pressure will always drop. Changing to a straight oil weight will only help until the oil heats up. The problem with a straight weight oil is that it's harder to turn the engine over to start, and the most engine wear occures durring start-up. Modern multi-weight oils give far superior lubercation than straight weight oils during start-up. How old/dirty is the oil in the engine now? Clean oil will help.

 

A high volume pump will also increase pressure because it will be pumping more oil. But it is not a high pressure pump. My high volume pump keeps cruising pressure at 58-60, and when it's cold, I can push 88-90psi if revved up. Warm idle pressure is 25-30

 

Oil pressure did pick up after putting some Lucas Oil Stabilizer in it.

The engine oil has about 1000 miles on it and looks brand new still. I plan on changing over to 20w50 Brad Penn oil and a Baldwin filter. I have heard the Wix 51515 (what I am running now) can drain back a bit and cause some dry starts. I believe someone either gave this engine a half-assed rebuild or didn't do a very good job of it. It has a few noisy rockers/lifters. 1 rocker arm on either side has a bit of side to side play, but I don't know if that is normal on these non-adjustable style rocker arms.

I had to change the intake manifold gaskets and when we pulled the intake and valve covers off, the engine was super clean inside. Like, fresh out of the hot tank clean. We also stuck a boroscope down the cylinders and found very fresh honing. Every gasket (intake, valve cover, fuel pump,) I have changed so far have been fel-pro gaskets, so someone has been all over this engine.

 

See what the thick oil does, and if you're still worried about it, install a high volume pump.

 

Since the rear main is leaking and with low oil pressure it is possible that the engine had a "in frame" rebuild and the cam bearings are worn.