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I have a 94 g20 5.7 v8 and when my engine is cold I have no problems idles fine oil pressure is right in the middle. But after the engine is warmed up to running temps the oil pressure at idle only goes to the red and my engine will Rev up bringing the oil pressure up but then it drops. So this causes a cycle of my engine revving up to keep the oil pressure up. Could this be low oil? I did just change the oil and put 5 quarts in and need to top it off again. But I also had this problem before I changed the oil.
You need to check for leaks. How many miles on engine/van. How many since the oil change?Unless your burning or leaking oil you should not need to to it off. When the pressure drops do you hear a rattling sound from the motor? If pressure is super low the lifters will be noisy. You really need an accurate pressure reading. You can install a pressure gauge that reads in actual pressure not just in the red or black. You can also borrow a pressure tester from autozone to get a true reading. Rule of thumb is about 10 psi of oil pressure per 1000 rpms the engine at operating temp. So idle should be around 10 psi.
I had the same problem with mine has a ton of miles on it I thought maybe the pump was going out so I put a high volume pump in it and when it took it apart I saw how bad my crank bearings were. Since I don’t have a lot invested in it I pulled the crank ( which is way worn) clean it up and put new bearings, now running down the road I have around 60 pounds and when I stop she drops to 5 for and second then pumps up to 10-15, she makes some noise but will probably last me a long time but I think next year I’m going to long block her.
I actually bought an e250 a couple months ago, the guy said the only reason he didn't drive it anymore is because he couldn't afford insurance,it sounded great has some killer oil pressure @20 down the road it lost all oil pressure..lol $200 tow later only 5 miles away from home ,pulled the drain plug and much to my surprise it smelled like I was doing a differential service..lol I guess what I am trying to say is snake oil won't fix low oil pressure. Like Blackbird said pump and bearings will get you by.
The engine has 86,000 miles oil change was at 85,000 by previous owner at a shop, did routine oil changes. I changed the oil myself at 86,000. Oil had no problems looked fine, no smell or anything. I don't have a tachometer on it. And the oil pressure drops to about 8 pounds at idle and then it revs and the pressure goes to about 40 then it cycles back and forth.
Bad oil filter ... may be new but its bad
I agree frscke1. Very well could be just a bad filter.
Yeah I bought a mobile 1 high performance filter when I replaced oil so could be bad, should I just replace the filter and see what happens?
Wouldnt hurt. Gonna need a qt to top it off. I forgot you mentioned that you had the problem before you did the oil change. You also could have blocked return passages.
Do you have oil cooler lines to your radiator ? May be a clog there also.
How would I go about finding if or where there is a clog?
It sounds like you have owned the van for about 1,000 miles. Just a few questions for you.

It sounds as if when the engine heats up, the oil is breaking down thus the oil pressure is dropping.

When you changed the oil, did you change from a conventional oil to synthetic oil or vise versa? Sometime this can cause deposits to break free and cause issues (going from syn to trad oil)

Did you use the correct oil weight per owners manual?


What you don't know (as not to many previous owner's will tell you is they over heated the engine or ran it low on oil once and thus scored the bearings)
What you also don't know was how far was the van driven with low to no oil pressure from the prior owner.

Since you have owned it about 1,000 miles has the van used any or much oil during those miles?

In the past, you could do to a Caterpillar dealer and get a sample vile, and then drain your oil and take them a sample and they would analyse it for you for a fee and can tell in most cases if you have bearing issues or what by the oil.
Gee guys.
I've owned lots of factory stock 350 Chevys. Cars and vans. 8 pounds on the factory gauge at hot idle sounds about right. I've had 'em show that on the factory gauge and still drove 'em for over 100K miles with the pressure dropping at every idle.
Our GMC now has over 335K miles. When it was a about 295K it had a small oil leak that required removing the pan. While I was in there (because of the ease) I replaced the oil pump with a high-volume pump (and the required new larger pickup assembly). BTW, it was clean as a pin inside the pan. After there's no difference when she's warmed up, still about the last notch on the factory gauge at idle, 40K miles later.
Runs about 30 to 35 psi warm on the road. Never any noise. 5w30 or 10w30, full synthetic or not, Pennzoil, Quaker State, or Bell-Ray. I do run a zinc additive about every other change and a K&N filter. The filter is just because it's easier to get on and off.
Our '95 G20 has the factory oil cooler and only 60K miles. It shows a little higher at idle but not much.
I went from conventional to synthetic I'm pretty sure, to be honest I have no idea what the previous oil was, the van was my great uncles and he passed away and I bought the van at the point. I put the correct weight oil in 5w30 as that's what it said on the oil dip stick cap. But to be honest it could be something as small as a low idle setting, I'm looking to install a tachometer to check that and so I can monitor the engine as well. And to add on its only at idle, when driving its about 40-50 psi depending on what road and speed etc but I don't think it's too big of a problem, I'm going to top off the oil because I'm sure since I changed the oil it has burned some off. I have had the van for about 700 miles, I got it at ~85,500 and it's now at ~86,200.
Thats the thinnest oil there is ... try thickening up your oil ... you may be passing it thru your valve guides or rings.

When I change my oil (Mobil 1) my motor takes 8 qts ... 5 str 30w and 3 str 40 w. I run 2 qt Car Quest oil filters.
Technically, 0w-16, is the thinnest oil currently available on store shelves.

Some 5w-30 will actually be thicker than a 10w-30 at 100c degrees or at
Hths viscosity. High temp high shear, is representative of what is occuring in the bearings.
Again some 5w-30 can have higher hths viscosity than a 10w-30. Not all. The allowances vary fairly widely.

Oil level will have little to do with oil pressure, until it falls so low the available oil gets significantly hotter,thus thinner, or when it drops so low the pick up tube for oil pump starts sucking air.

In 2007, my oem op gauge was reading alarmingly low at hot idle. I installed a mechanical gauge, which revealed excellent oil pressure hot at idle.

If the engine does not start ticking or clacking at hot idle the op gauge is suspect number one.

If it is making noise hot idle, does the dipstick smell like gasoline?

Excessive fuel dilution thins oil, reduces oil pressure.

Actual low oil pressure at hot idle can be helped.with thicker oils 15w 40 or 20w-50. The 5x-xx and 0w-xx oils do lube better in cold weather with cold engine, but offer no benefits in warmer environment on older engines.

Dirty sludged engines might quickly clog oil filter, which might cause low oil pressure reading if the filter's internall bypass is not functioning correctly.

There is tons of bad info regarding motor.oil repeated over and over as verbatim on the internet and many self proclaimed experts are quite delusional.

I installed a mechanical gauge as it was cheaper than a one time test gauge.

If your engine is still smooth and quiet at hot idle, suspect the gauge first.

Step up oil thickness if it is noisy and know this solution might be short term.

Thickeners like .lucas 'oil stabilizer' have no detergents dispersives antiwear extreme.pressure friction modifying additives. LoS will duliluted those additives in a properly formulated motor oil.

LOS might also render the anti foaming additives in a properly formulated motor oil useless ,and the oil pump will then send frothy oil through the bearings.

Friends do not let friends send frothy oil through bearings.

Beware of marketing and well marketed products that have a cult like following.

If you want thicker oil to address low oil pressure at hot idle, buy thicker oil.

If you want to sell a vehicle with a worn out engine whose oil pressure reads too low, add lucas oil stabilizer to whatever is in the sump, polish your teeth and practice holding eye contact whilst lying.
I do not plan on ever selling the van. I also plan on fixing everything my self as it needs fixed. I will be buying a tach soon and installing it. Other than the oil pressure being low when the engine is hot there are zero problems. No engine noise, nothing. Very smooth and it hasn't given me any problems. I don't doubt there actually isn't any problem.
A tach is great. The Op gauge reading low, does not mean the OP is actually low, especially if no noises start when idling at hot idle speed.

I installed a mechanical oil pressure gauge well before I installed a tach. Both respond to rpm similarly with hot oil, when cold the Op gauge pegs at 66 to 68PSI and only begins to drop at lower rpm once the oil warms, and hot as it gets with 10w-30 at 525 rpm is 19 to 21PSI.

My OEM OP gauge still works as I T'd the line. the OEM gauge does not really correspond to the mechaincal OP gauge. there is a 45 second delay and much less of a range. So PSI reads one hatchmark above the bottom, 68 PSI reads just over half.

So do not put much faith in the OEM OP gauge. Its likely a bipolar liar on an overdose if Diazapam, looking for attention.
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