Valvoline 10w-30 and Purolator Gold

 

Mobile 1 Synthetic w/ WIX Filter or Mobile if you want to spend 7$ more.

 

A++ Wally world 15-40 fleet oil is also a good zinc substitute for Rotella. With the 4.0 tractor engine it will run forever with just about any dino oil...just stay in spec.

 

And here are the original factory specs for weights.

Jeep Engine Oil Viscosity

This was taken from pages 82 and 83 of the 1989 Chrysler/Jeep owners manual.

Selecting Engine Oil Viscosity

When changing or adding engine oil select the proper grade by using the chart on the following page. Select the grade that corresponds to the ambient temperature range you expect to encounter before your next oil change.

30*F to 100*F+ 20W-40 or 20W-50

0*F to 100*F+ 10W-30 or 10W-40

-20*F to 60*F 5W-30

 

I know you like quoting that page a lot but you do know that engine oil has changed in the last 24 years, eh? lol

My standard answer is "run whatever makes your Jeep happy". Just run bloody oil

 

Yeah, I know. But there's no fear in running 15-40 year round.

Filters are the big buggaboo with our's being mounted upside down. Have to have a filter that has a good anti-drainback valve. No cheap crap.

 

Eneos 10w40 full synthetic. Best oil ever!!