Abnormal oil pressure

hook4em

New Member
Joined
Dec 6, 2007
Location
Jacksonville, NC
4.0l inline 6 w/112k miles. When engine is cold and at idle oil pressure is around 40. When engine is at operating temp engine oil pressure remains at 40 while driving. Drops to 10-12 when at idle. Recommendations? :confused:
 
Does it knock? are the lifters making noise ?

if not, drive it. You would be surprised what minimum spec for oil pressure is on most engines.

If it really bothers you, change the oil, use a heavier weight oil ( 15w40 is a decent choice )
 
My 4.0 did the same thing until just recently. I installed a new oil pickup and changed the oil and now my pressure is higher. I get 60 when it's cold and I'm not even sure what I get after it's warmed up. I broke way too soon on my last trip. :(
 
Thats normal oil pressure for a well broken in motor. Around 10 psi per 1k rpm is a good rule of thumb. As long as it rises with the rpms you are fine, dont just run a heavier oil
 
I paid for the AllData subscription, so I figure I better get my money's worth out of it. I looked it up for you and AllData says for the 2000 TJ with 4.0: Minimum oil pressure at idle is 13 psi.

If you are reading 10-12 I'd say you are within the instrument inaccuracy of the gauge and are probably good.
 
245K on my I-6, does the same thing. Give it a fresh oil change and it'll go back up. then as the oil breaks in, you'll see it settle back in to a lower reading at Warm Idle. Heck I've gotten to where I can read my oil gauge and know when I need 1 qt of oil or an oil change. :D
 
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