fluctuating oil pressure - idle vs drive

[jvangun]

I did a quick search and couldn't find anything specifically related to this. I just noticed today that when the truck is idling the oil pressure is just over a quarter but as soon as I start to drive it goes up to about half and then back down again to a quarter. Is that normal or something to be worried about? I have to take it in tomorrow to have the squeaky belts and a busted sway bar bushing looked at and wondered if I should have this checked as well. If so, what specifically would they be looking for?

Thanks in advance.

 

[APKhaos]

The lowish pressure is OK at idle. The pressure going up to something north of midrange on the gauge is normal. The pressure then falling back to a low reading while you are driving is not normal and is cause for concern, so lets get it straight about what you are seeing.
- When you at a normal highway cruise at say 3000 RPM what is the indicated oil pressure?
- When you accelerate from a stop, the pressure gauge moves up to north of midway, is that right?
- Assuming constant speed at say 2500RPM, how long before the indicated pressure drops down, and how far does it go?

You have checked the oil and filled to the Full mark on the dipstick, right?

 

[Brock]

x2 will be lower at idle and go up while driving...that is normal. Ensure oil levels are within acceptable ranges and dont worry about it. Just be able to recognize normal readings so if it changes all of a sudden you can take notice and investigate.

 

[Nottajeep]

If you have an owners manual, the info is very clear about oil pressure at idle vs driving.

 

[jvangun]

Thanks for the replies. Yes, oil level is normal. Specifically to the questions from APKhaus, it is 1/4 at idle, 1/2 when I am accelerating, and then 1/4 again at next idle. Appreciate the quick replies.

Thank you.

 

[paflytyer]

Thanks for the replies. Yes, oil level is normal. Specifically to the questions from APKhaus, it is 1/4 at idle, 1/2 when I am accelerating, and then 1/4 again at next idle. Appreciate the quick replies.

Thank you.

That sounds perfectly normal.

 

[12guns]

Yep, normal, mine does it too. It did catch my eye as well, but nothing to worry about.

 

[GaFJC]

This is likely a coincidence, but after changing my PCV valve my oil pressure gauge has started acting wonky. The reading has gone from previously moving quickly from ¼ at idle to ½ at roughly 2500 RPMs to slow movements of a steady ¾ at both idle or at higher RPMs to just above ¼ when warmed up.

These new gauge readings are within norms but still odd as it did NOT do this before, ever.

Here is what I’ve done when my 100 series OCD kicked in:

1. Just to be safe I replaced the new OEM PCV with another new valve and checked all related hoses. All are good. The “new” gauge reading is still present.

2. Replaced original oil pressure sending unit with new OEM model. Gauge still showing “new” reading.

3. Changed oil although previous oil and filter had less than 2500 miles. Color and levels were perfect (and so were Blackstone reports from less than 6k miles ago). My thinking was a slightly collapsed oil filter. No change as “new” gauge reading still present.

4. The steering rack ps D bushing was replaced about the same time. Thinking an oil cooler line was accidentally pinched I checked but everything is fine.

5. I’ve ordered an oil pressure test gauge. Will test this weekend.

6. No other odd behavior (mine or the 100)

Is the gauge malfunctioning after 143K miles? Any other items to consider?

 

[TXLX100]

A lot of people have reported wacky oil pressures in their 100s including myself. I would probably go ahead and buy a new oil pressure sending unit to replace the old one after you take the pressure gauge off and it says it's fine. I had a GM 350 in a boat I had to replace the sending unit in every few years after it would fail or get gunked up. If it's the same technology in the 100 part, it probably just needs to be replaced.

 

[GaFJC]

A lot of people have reported wacky oil pressures in their 100s including myself. I would probably go ahead and buy a new oil pressure sending unit to replace the old one after you take the pressure gauge off and it says it's fine. I had a GM 350 in a boat I had to replace the sending unit in every few years after it would fail or get gunked up. If it's the same technology in the 100 part, it probably just needs to be replaced.

I replaced the oil sending unit with a new OEM model after the gauge started acting funny.

 

[GaFJC]

Any suggestions MUD'rs before I hook up the oil pressure test gauge in the morning?

 

[GaFJC]

FYI to those who may encounter this issue, an oil pressure test gauge showed warm idle at 25psi and 3000 rpm was at 75psi.

FSM says 4.2psi or more at idle and between 43 and 85 at 3000 rpm. While I am 20 psi above the min FSM idle psi, I don't believe it's an issue as the FSM states " or more". I hope....

I can only guess my stock gauge decided to show a different personality.