What brand and weight oil do you guys run in your 4.0s? Also which is best for an auto transmission and transfer case? Thanks

 

I use Castrol GTX 5W-30 in mine. For the tranny Dexron II which is also the FSM recommended TC fluid. I'm going to replace my TC and diff. fluid this week. The diff uses API GL5, various wts. 90 - 80W-140 . The manual shows a chart for recommended weight for temperature/towing etc.

 

Be sure to use a good quality oil filter or you can "dry-start" your engine starving it for oil initially. Some oil filters have pi$$-poor anti-drainback valves that cause this. Wix or Napa Gold are good filters and reasonably priced and readily available.

 

Thanks for the info, i typically use Fram or Wix filters... Yea i know alot of people cuse Fram filters, but they are what ive always ran on my race motors aside from Wix and ive honestly never had a problem with them.

 

I'll bet your racecars don't have the oil filters mounted upside-down or sideways like the Jeeps. That's why we need excellent anti-drainback valves. Fram doesn't have those. Wix does.

Here's a good read on oil filters.

http://minimopar.knizefamily.net/oil.../opinions.html