I Really want to use a Exotic/Foreign Motor oil for one of my 4.0s. I have to decide soon, between two oils, LiquiMoly LongLife 0w-30 or 0w-40 and Motul 300V Chrono 10w-40 or Trophy 0w-40. OK, I quess decide between 4 different oils, two diferent brands. LiquiMoly is made in Germany, Motul is from France. I Already have Experience using German Castrol(0w-30), which is Made In Germany, Castrols only True(Group 4 or Group 5 base oil) Synthetic. Proabably going in either a 64,820 mile 2001 4.0 or a 250,588 mile 96 4.0 in front of AX15. Help me Decide. Oh wait, this isnt bobistheoilguy...

stop.

the 4.0 isnt some engineering marvel that needs stupid expensive oil. if you want to run synthetic, i recommend shell rotella t6 5w-40 (which is what i run, and its great. waiting on my blackstone report after a 5k change) or amsoil z-rod. both have high zddp levels. otherwise youre just throwing your money away... a zero weight doesnt belong in a jeep unless you live in the arctic.

You're not driving the space shuttle, it's a Jeep for crap sakes!

If he can afford to spend the money on fancy foreign oil, why not try it? I do agree with not using the zero-weight oil though, no reason for an XJ to use that thin of oil, it might even cause some leaks you didn't even know existed! Although I would definitely agree that the money that you are spending on more expensive oil could be better used elsewhere, it could be interesting to try it, and report back what you found. Just be prepared that this foreign oil may end up having little or no benefit, except for saying that you have fancy German/French engineered oil in your tractor motor 4.0.

the "exotic" oil may not have the additives that a 4.0 needs, rememb er these are two completely different deign styles. the 4.0 needs a good bit of zinc to help it live a long life. the shell rotella has that. i run the 10w30 shell rotella synthetic blend and have been using it for the past 45000 miles with great results. my current 4.0 has 190k and runs like new.

Hammer time.

its not 0 'weight'. it's 'winter'. and you can run zero winter in a jeep year round...i do. as far as weights go, i keep it to 30 now. i had rotella 0w40, but switched to 0w30 this past change. my mechanical oil pressure was too high for my liking, and too high of oil pressure will wipe your bearings. too much cohesion, not enough adhesion. on the gauge i was getting over 80 psi at start up. now its closer to 65-70, depending on outside temp and whether or not i plugged it in the night before.

i agree. there are gas bearings (compressed air) in space shuttles. but jeeps use plain friction bearings just like every other car out there too. happy bearings equal long life.

Most modern oils are approx 10 weight at NOT, or Normal operating temp.
The difference between dino oil and synthetic is the molecule size. With dino oil they differ, whereas the syn. has equal size molecules.
There are syn. oils in the US that have the rating that BMW/MB/Vdub/AUDI require. M1 0W-40 is an example, Pennzoil Ultra 5W-40 is another. Pentosin and Amsoil both are certified.
IMHO, unless you have a bunch of money to spend and are actually getting your oil analyzed, then there is no point in running these "exotic oils"

Gas bearings? I did not know that. Sounds interesting, I will have to see if I can read up on that for curiosity's sake.
Is there anything wrong with mobile 1 full synth 5w30 in my I6? The manufacturer recommends 5w30 so what are the advantages of deviating?

The weight of oil you run depends on climate. If you are in a warmer/hotter climate, a thicker oil such as 15w40 may result in better lubrication. For someone in a cooler climate, an oil such as 5w30 will ensure that the oil lubricates all necessary areas when it is cold, but will also still have proper lubrication at operating temperature. This is outlined in the Jeep FSM (at least for 1989 it is).

U can't touch this.

Man you guys got TROLLED

How's that? Pretty sure the 4.0 gets to the same operating temperature wherever you drive it... "Acceptable viscosity" != "Required viscosity"

Yep, the lower, or "winter" number only means something for its ability to flow when cold. A 0 weight will flow faster at 32 degrees than a 10 weight. So if you live in a very cold place you want the lower weight for cold starts, but if you live where normal people like to live you use a higher weight. I run 10w40 all year because it rarely gets to below 40 degrees where I live.

This ^^ is what I was attempting to explain.