I've had oil pressure fluctuations in the past month or so. When the car is warm it will idle around 22 psi. If I rev it up it will go up and come back down slowly but it will fluctuate around 30 psi for a while then come back down to 22psi and stay pretty steady.

After I changed my oil today I was driving around a turn and I gave it some gas and got alittle sideways. I looked down and I had no oil pressure. Oil level is fine. I used mobil 1 10-30 with a ac delco filter 1218 (the bigger one). Anyways, I turned it off right away and restarted and the oil pressure was fine. I also noticed that at WOT the oil pressure will go up to 60 then once i get around 4500 it will drop about 10 psi to around 50.

Is it a sending unit? Autozone has 2 different sizes, which one should I get?

 

It sounds like it may be the sending unit...

 

Hopefully. It was pretty scary looking down and having no oil pressure. I didn't find any metal shavings in the oil and no weird noises so thats good. Any idea on which one 1/8" X 27 or 1/4" X 18 threads?

 

I think it goes like this:

1/4-18 threads for 1993 and some 1994s that are located above the oil filter

1/8-27 threads for 1994-1997 that are mounted behind the intake.

 

We'll guys, the sending unit fixed the fluctuations. But once the oil is hot I'm not getting the psi I'd like to get at WOT. When I'm WOT the pressure will climb to around 55 then slowly drop to about 35 when i get to 5500rpm. Do you think my bigger filter is stealing psi's? Its the ac delco 1218 thats used on the 5.7l trucks. Should I use a thinker weight oil? maybe 10w-40. I just changed my oil yesterday so I really don't want to spend another $30 to change it again. Should I try putting a smaller filter and putting in 2 quarts of 20w-50?

 

One thing that I've read is that at WOT in the lower gears...1st and 2nd for an auto...1,2 and 3 for a 6 speed, the rapid acceleration shifts the oil away from the pickups and causes the pressure to drop...but my car seems to be ok at WOT...so I don't know if thats true....

 

Aren't the pickups in the back of the pan? When I took it up to 5k rpms I didn't have it at WOT so I don't think its a problem of oil shifting. Do you guys think I should remove my oil cooler? Or just run thicker oil in the summer? Do you think its hurting the engine to run it at 5k with only 35-40 psi's?

 

94Green...I also think the pickups are at the back ... I never said I agreed with that its just something I read here in LT1Tech so figured I'd let you know the possibility...once again I haven't had that problem and neither has at least one other friend of mine driving an LT1...

 

Do you add extra oil with the big filter? If not (or even if you do), you might consider adding half a quart and see if anything changes. That might help determine if it is a pickup issue.

 

I changed my oil pressure sending unit, the stock one broke. I was getting lower readings with the new sending unit that I got from Autozone. I think you'll be ok with 10w30.

John

 

Thanks for all the help guys! I just drained a quart of 10w-30 and added a quart of 15w-50 and my oil pressure while standing still and hot at 5k is around 50 psi. So it went up some. From what I hear most people are around 45psi at WOT, so I'm satisfied.