What is a normal oil pressure reading once
engine is warm and it is idling?
What I consider good oil pressure after warm up is 40 to 45 pounds of pressure at idle
Yes, around 40 lbs is norm, but but if she holds at 30 lbs. and rises when rpms are brought up, it is ok. May want to consider putting in a high volume oil pump if there are a lot of miles on the engine. The rpms at idle make a difference at where the oil pressure is reading also.
I have oil pressure at 30 rises when accelerating but sometimes it drops to between 25-30 causing the motor to knock slightly in park. if i put it in gear the knock is gone .while stoping it will have the knock until the transmission has the pressure on the motor if that makes sense. Does it sound like oil pump or rod bearings or both .ive also heard of the piston slap but that would be louder id imagine. Thanks for reading any suggestions .
If you have a cracked flywheel or loose bolts on the flywheel it will sound like a knock as well. My jeep and one other started knocking because of a melling high volume pump. Put a stock pump back in and knock was gone..
Take your oil pan off and check your oil pickup. Mine was clogged to hell and would hold 30lbs and wouldnt rise. Cleaned pickup now rises up to 45lbs. Mine also had a slight knock before cleaning the pick up.
My 1996, XJ, 4.0L with 240,000 miles on it run down the road at 40 psi....when idling it will drop to 20 psi. I have no knocks or rattles. I run AMSOIL 5w30 synthetic with a 25,000 mile or one year oil change interval. At one year I had driven 17,000 miles. I sent out an oil sample for an oil analysis; the oil was still good so I just changed the filter (added a quart of oil) and drove it another year.
98 Jeep Cherokee sport. At start up it’ll stay around 40 at idle. After warm it stays around 20 then Shoots back to 40 under load.
My ? It’s goes high then drops to 40.
I have done a bit of analysis of this issue. I have run 3 different oils each on a 12k mile interval in my 98 XJ. First time I ran my normal (at that time) oil which was M1 high-mileage 5w30. 1/4mile time (I have a sleeper XJ that I tow behind my DD also) 17.4seconds. This burned 3 quarts of oil extra over the cycle. Oil pressure was 22- 25 at idle, max at 48. Quarter in 17.6s and a little more valvetrain noise that normal. Second time was Autozones conventional 5w40 burned 3 quarts, 20-23psi idle and 48 max. Third time was T5 15w40 25-27psi isle and 54max. Quarter in 17.7 and more valvetrain noise. My current oil change is 1q Rotella, 1q SN+ (Oil for Direct injected engines), and 4 quarts of M1 normal full synthetic (not high mileage) 5w30 oil pressure at idle is a bit higher than M1 but max is the same.
I also should add that the Rotella only burned 2 quarts in 12k miles which is conducive with heavier oil. Also, the only Dyno numbers that I have are with current oil setup and it’s 147rwhp and 179rwtq. Sleeper has a cammed aluminum 6.0 LS making 400/490 at the rear wheels. 12.8s quarter. I want to get new pistons and nitrous but I might as well build the whole bottom end.