oil weight ?

[project88mj]

what kind is the 4.0 made to take?

[project88mj]

c'mon guys i need the help?

[comancheman]

i always run 10-30 6 qts for the 4.0

[offroader461]

i run 10W-30 valvoline

[DirtyComanche]

10w30 is probably the best option. But it varies by climate, intended use and engine age.

 

 

 

But I'm not an oil guy.

[Oizarod115]

10w30 in mine, brother runs UP TO 20w50 in his to get his oil pressure to rise a little bit (really bad oil pressure.)

[project88mj]

well i got 213K on the motor and do alot of higher rpms (3,500+)

will 10w-30 work fine or synthetic?

[JeepcoMJ]

10-30 high mile synthetic

[project88mj]

could you tell how will it help ?

[JeepcoMJ]

no clue, it's in the chemical makeup...it doesn't break down as fast and helps to reduce anymore buildup of gunk in the engine, and clean it too i believe.

[Pete M]

Or you can just use any ol' 10W30 oil and change the oil regularly. :D Don't skimp on the filter though. Buy a good quality filter (meaning don't buy the cheap ones or a Fram).

[Eagle]

what kind is the 4.0 made to take?

The old ones were supposed to use 10W30 or 10W40 (both were listed in the FSM). The newer ones are supposed to use 5W30

 

well i got 213K on the motor and do alot of higher rpms (3,500+)

will 10w-30 work fine or synthetic?

How's your oil pressure? If you're getting 40 psi or better at highway speed with the 10W30, it's okay. Personally, on a high mileage engine I would be using 10W40 or a wider range synthetic. In my '88 XJ I'm at 265,000 miles and I run Castrol 5W50 in the winter, 20W50 in the summer.

 

And you shouldn't be running a 4.0L above 3,500 RPM a lot. Especially not an '88. The torque peak is WELL below that. You're just beating up the engine for no purpose. I doubt that mine ever goes above 3,500 RPM. My normal shift point is 2,200 RPM.