After wheeling my jeep for about an hour yesterday my oil pressure went from chilling at the usual 40 to about the last notch before the first at idle but went right back up to 40 as soon as excelerating. Is this normal for us 4.0 guys cause my budys zj was the same way. It was fine 2 day Just curious as to why oil pressure drops after a while of driving?

 

Yeah my oil pressure when cold ranges from 40-60 psi depending on how cold it is here in Chicago. Once it warms up it idles between 18-22 lbs and during acceleration can reach 40 again but once it shifts into the high gear it drops between 25-35. It has me worried. I put a external gauge where the sending unit goes from Harbor Freight today when it was warm and at idel it read 10 psi and at 1600 rpm it only went to 25psi. Sounds low to me. Is this similiar to what your seeing on yours?

 

yeah when it gets hot after a while it will go to about 13 or so when idling but that is normal on the 4.0

 

OK so 13psi at an idel is not unheard of, how about going down the highway at 55-65 miles per hour? I think mine is about 35-38 psi at 1800-2000 rpm?

 

Yep same thing....must just be a jeep thing, only does it after about an hour of driving

 

Ok, thanks for letting me know. Currently I have 10w-40 in it. Has anyone tried thicker oil like 20w-50 to see if it would increase oil pressure?

 

Yep on the 20/50 (Castrol) and no it didn't do anything for the oil psi ,180k on the motor.

 

Wow no difference with 20/50. Thanks for letting me know.

 

i use a 15 50 Mobil one on mine and a get a little boost in the psi on mine goes from about 40 when driving to about 45 and idle went from about 13 to 16 at idle. but it might not give the same results to every one

 

Since the oil pressure seems much better when the engine is not at normal operating temp I wonder if a oil cooler would make much difference. I've seem some that have an adapter that fits between the filter and filter elbow. From there you can run line to the cooler mounted in front of the radiator.

 

in wormer weather strait 30

 

Ya im running 10W30 castrol with a bosch filter

 

yeah i have been thinking about putting a oil cooler for when i am out trail riding so it will help keep the oil from gettint to hot and messing with the oil psi