my 88 f150 has a 5.0l with 5 spd tranny. oil pressure is at 5 psi on idle (i have mechanical gauge) on cold start up it is at 40-45psi but once it warms up and idles its down to 5-7. when driving and my rpms are at around 1800 my oil pressure is only like at 12-15psi. any ideas? oil change brings it up a few psi but thats it

 

Worn rod and main bearings most likely. How many miles are on it?

 

I'd check the oil pressure with another "known good" gauge and see where you are at… that way you are sure it really needs internal work.

 

i was thinking that as well. the engine has around 130k on it. it doesnt knock or anything. no weird sounds on start up. im thinking about takin it in and putting a new oil pump screen, oil pump, oil pan gasket (has a small leak on the pan) and new main bearings. just trying to bring some life into her. she runs great though, no lack of power or anything. so im thinking compression is good especially with low oil pressure

 

i will have to find another. can i just switch the gauge itself and leave the copper line in? i dont wanna get underneath again and try changing the copper line

 

There you have it. It ain't broke!

You may have heard about the " idiot gauge" that the Ford oil pressure gauge became. Quite simply, Ford got sick of all the criticism about low oil pressure at idle and the resulting expensive warranty claims. They rigged the gauge to read mid scale and used an idiot light sender that did not kick off until pressure was very low.

There is a lot of video out there showing engines running without oil and the truth is they will run at idle for a very long time without damage. The fact that oil is still flowing, even at low pressure will protect your engine and I would prefer the increased flow and reduced frictional losses of loose clearances over high idle oil pressure anytime.

Bottom line, it's by design. Don't worry about it.

 

I was gonna say what not'nuf said. . .low pressure at idle doesn't necessarily mean it needs internal work. As long as pressure builds, I wouldn't worry.

If it gets worse/makes noise/causes sleep loss, a bottle of the thick Lucas will increase psi.

 

oooooh well thank you so much for clearing that up. my aftermarket gauge said 5psi so i was like wow thats low. do you think it would be okay to switch to 10-30 not that its warmer or stay at 5-30? i use the motorcraft synthetic blend stuff with a motorcraft filter

 

what if my rpms are like 2k and pressure is at like 12-15psi? im starting to think getting that aftermarket gauge was a bad idea lol. im starting to worry. i love my truck and dont wanna see her go. put too much wrench time into her

 

I'd personally just stick with a conventional 10w-30 OR 10w-40 oil. 5w-30 for winter use only. Stay away from synthetic blend and straight synthetic as this will also drop your psi by a few numbers. They are smaller molecules and therefore slide by even more when tolerances are not as tight 100,000 miles or 50,000 miles ago. Just saying..

Be sure that you use a Motorcraft or Wix, even Napa filter. Stay as far away from Fram if at all possible!!!

12-15 psi should be ok. I'd let sleeping dogs lay and just do regular maintenance as needed. If it really bothers you, open your wallet up and spend around $1500 for a complete rebuild and see comfort with 25-30 psi @ idle.

 

would the castrol conventional be okay? i always use motorcraft filters. the castrol is always on sale here so yeah

 

Yeah, that should be fine. Any conventional motor oil such as Castrol and many others should be fine. Literally, I either buy Super tech or what's on sale! They are all doing the same thing and I'm not fatting oil executives wallet's any more than I have too.

 

hmm now that i know that you guys keep saving me money with every thread