Ya, so I been reading alot.
Got an 01 4.0 xj new to us, like 160,000 on it. It's our first oil change in it
Wife been driving it to her new job 3 miles
It's freakin cold here in Michigan, single digit's!
oil pressure was really good 50psi untill we hit this weather now it's really low this morning, 15psi. I told her she can't drive it like that, Should I run a 0w30 with these short runs twice a day or 5-30

Got it drained out and started second guessing myself what I should use.

It's got a mopar filter which is what I run in other xj's

 

5w30 year round here and we get -10 -20 every couple weeks, no issues.

 

5w or 0w 30 or 40 will be fine. I run 0w40 in everything that will take it.

Low pressure like that is odd. It should be very high when it's cold. Is the sending unit (above the filter) leaking oil by any chance?

 

5w30 dino year round

90f summer
-40f winter

 

Yeah, that's not good. Might bypassing the filter?

 

So I changed to 5w-30 with new Mopar filter, I'm Thinking maybe the oil was older than i was told, Still Low oil pressure, Bout all I could get done before dark today. cold!
I'm thinking the sending unit may have cracked in the cold, Got a spare motor out back I'm gonna pull the sender off and replace it, It wasn't gushing oil or anything.
It pulled oil into the filter on first try and had to add a little more to get on the mark. So I think I'm getting pressure. Just happened over night like that?
Gotta be a bad sender? it was at 12psi after the change.

edit- No oil leaks

 

When I had a question about my oil pressure readings, I dropped by the auto parts store (Pep Boys) and picked up a mechanical oil pressure gauge. Took about 5 minutes to install it and get a reliable reading to compare against the dash gauge, and take it back out. Now I know.

"Know" is a good word.

Cost me 16 bucks, and I keep it around for such needs.

 

Thanks Man, I do need one.
Telling her she can't drive it like that started some **** in a hurry, know what I mean...

 

Obviously too late now, but I don't EVER take the PO's word for it when it comes to when the last oil change was done. I don't care if they told me they just changed it, I'm changing it.

But good point on the oil filter, I've noticed different readings in similar weather depending on the filter I use. It's very likely that the sending unit is shot, they're only good for 10 years or so before they crap out or get wildly inaccurate.

 

Yep. I ran out of my usual (Wix 51515) and had to grab what they had at the auto store. I went to TWO stores and could not find anything except the short ones, and my pressure is running higher than usual.

 

Running 10-30 rotella year round. Had my wife take hers to the shop in town for an oil change once and they used 5-30. I didn't like the way the motor sounded with it. Sounded the way it does when it's about due for an oil change while running 10-30. Temps from 0-100 here.

And as far as taking PO word for oil change. No way. I've had some tell me they just changed it and it was black as night. Just wipe some on a paper towel and give it a good sniff and that's all you need to tell if it needs changing.

 

Well it had a sticker in the window when we got it and po said it was just done, So I didn't really question it a lot ya know... It had great pressure everyday till I hit 8* It looked fine, smelled good! still not burnt, Dark sure but no smell.
and it was a dealer sticker now that I think about. I know the shop.. But I hear what ya'll sayin!


Pressure gauge for me in the morning, It Looks pretty new and worked fine, They just crap out like that? Literally over night? That's why I'm hoping it's just cracked.

 

Prolonging an oil change a couple thousand miles even won't cause a 30 PSI drop in pressure overnight, lol

Filters indeed do make a difference, however in the opposite way. In these engines the pressure sending unit is downstream of the filter, so when the bypass valve is open pressure will go UP as the oil pump is pushing against the sending unit harder without the filtration media in the way, and when it closes there's a drop. If you pay attention to the gauge you can see this behaviour as things warm up. A super clogged filter or non-functional bypass will cause a lower reading (or internal wear of course).

You could certainly try another filter. Doesn't cost much. The mechanical gauge is an excellent idea.

 

So the mechanical gauge said I was good at 38, Today. So I switched the sender w/another it was good 42 at idle. rock&roll

 

It's good to know.