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Low oil pressure on my 258

7K views 13 replies 10 participants last post by  LumpyGrits 
#1 ·
Hi.
when hot, engine used to give me about 17PSI@1000RPM and about 35PSI@2000RPM
on the way to the last trip, it dropped to 24-26@2000.
After the trip (Amazing 3 days deep in the desert, about 260KM), 20-22@2000

when RPM is about 1500, it reaches top. after 1500 it drops up to 2-4PSI

Gauge is a mechanical Bosch.
Oil - penzoil gold 15/40
Filter - AC-Delco.
Engine - 258. I believe a 80's
I do know that the main bearings are tired, but such a quick drop is a big concern

Thanks
 
#2 ·
change the oil first, inspect the oil, fuel, water, particles, HEAT as in desert can be a real stress on oil. Being anal I would confirm the gauge on vehicle - attach a simple
mechanical for a second opinion...
 
#4 ·
15w40? good lord!

I read all this about using thicker oils in jeep motors and it was terrible advice on here. Lifter noise, especially in the cold. Switched to Mobil 1 5w30 full synthetic in a rebuilt with 6k and she runs beautiful now with no ticking. AC Delco oil filters.

Try another gauge as well, I have an electric one that goes up and down non stop lol.
 
#5 ·
What's wrong with 15W-40? I've been running that grade in my Jeep for years. FYI, my 1980 Service Specifications manual lists SAE 30 or 40 as recomended single viscosity, or 10W-30, 20W-40 or 10W-40 when operating in temperatures above +40 degrees F.
 
#8 ·
According to Chrysler the acceptable oil pressure is 7 psi per 1000 rpm. My engine sits around 14 psi at idle and 43 psi going down the highway. This was recorded with a mechanical gauge. My gauge in the Jeep is off from the mechanical gauge. I also run 15w40 Amsoil.


Sent from my iPhone using Tapatalk
 
#10 · (Edited)
Outside temp is about 25c currently.
Engine temp is about 80c.
I run with a 82c thermostat and 2 speed electric fan (77-82/82-87 Volvo 940 2.3T - 3500CFM).
Fan high speed is rarely engaged.

at winter, the coldest temp should be about 4C
at summer, hottest temp (which i go outside) is 35C (when it's hotter, i stay in the AC)

Height at home - 560m
Highest hight i can go, about 1800m
Lowest point, 400m below sea level (the dead sea)
 
#11 ·
you guys are running this thick *** oil and getting less oil pressure than ours running 530 :D . All that thick crap did was offer engine noise. A little over 50psi at 65-75 MPH with 5w30. I spoke with a mobil one tech and they suggest that if you want to run a 40 weight oil, run 0-40 for hot season. We'll stick with the 530 oil in ours.

I want oil to get up there quickly, not sit and slowly make its way up.
 
#13 ·
The paper work that came with my rebuilt engine and the TSM both say use HD 30 or as an option for temperatures that never get that cold around here 10W-30. I just assumed that both must have known the best type oil to use. IMHO the key to keeping an engine healthy is changing the oil on time and based on the driving conditions you encounter. I also believe that it is important to get the engine to proper operating temperature and drive it for several miles on the highway to prevent sludge build up.

I change my Jeep's oil every 3000 miles or once a year which ever comes first!
 
#14 ·
32+ years run'n 20W-50 Castrol is all the proof I need. This weight oil is spec'd in the owner's manual.....
At idle, the engine shows a steady 18hg(2700' ASL)on the V-gauge(almost no needle movement)and runs as good as the day I bought it in March of 1985.
My mechanical SW oil psi gauge shows a hot OP of 25psi at idle, and 60psi at 2600 rpm. My gauge is within +/- 3 psi of a certified FAA oil pressure gauge.
I have never been inside the engine other than to reseal the valve cover a couple of times.
LG
 
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