What are some advice on what oil to use? Also what are some good and relatively cheap mods that will help with longevity and mpg?

 

6 liters of 10W30 motor oil and a fresh filter.
Lots of brand debates here, lots of debate.
The important thing is change it (oil and filter) regular, brand is less important.
Every 4000 to 7000 miles (8000 to 10000 km). More often if only town driven.
Change if you have any water exposure (milky oil appearance).
Did I mention change regular is the key element here to longevity.
Don't rev the heck out of it!
The Peep just rolled 670000+ km, speaking from a bit of experience.
That 4.0 will run like a top forever.

 

Do a quick oil change (drain the oil and change the filter) using whatever cheap brand of 5w-30 you want a bottom-of-the-barrel regular FRAM filter. Run the engine for about 5 minutes and then change the oil again (the first change was to make sure all the old dirty stuff was out) and for the 2nd go around use Rotella T6 and a '79 Ford 302 WIX/NAPA Gold filter. Use Rotella T6 and WIX/ NAPA Gold filters from here on out.

 

I wouldn't even use a FRAM for a quick change like that, you can get a Purolator Classic or Motorcraft FL-1A for around the same price as a FRAM and they are much better and is less likely to cause pressure issues (granted I doubt it would do any damage in 5 min but why take the change) or get an STP or "store-brand" filter, they are as good or better than the cheap FRAM (the cheap "orange-can" FRAM is literally the worst filter you can buy) and even cheaper.

 

This is the only time I suggest a Fram (JUNK jilter) or the "cheapest" even better store brand for the first go around also the oil. Excellent post.

Then use the search function here there are literally weeks of reading on the subjects you asked about. I'm not trying to be a Smart *** either just saying a wealth of information for you "good info".

 

Agree 100%
I've owned 5 jeeps with the 4.0 and each get the t6 treatment

 

Thanks so much for the reply guys i have currently 156 k on her. and want to keep it for a long time.