[1BadJeepX06]

Either Pennzoil 10W30 -or- Mobil 1 10W30..

Pennzoil - because my dad has a chevy truck with 483,000 miles on it that has had nothing but Pennzoil in it since day 1. Still running strong...

Mobil 1 - because this is what I ran in my last vehicle. It was just another oil to me, I really didn't notice too much difference. Mobil 1 supposedly cleans out your motor of carbon and gets black quick. And until your motor is "cleaned" out it will need changing frequently. So if I run it, it will be on the first change before my motor has a chance to "carbon up" on the inside....

Honest opinions here. These are my two options... Keep in mind, it is a new Jeep with only 1,200 miles on it...

[daveg13]

I personally can't justify the 3-4X in cost with synthetic. I've always used dyno oil and changed it at 3k miles and never had an oil related problem.

[UCTJ]

I use and recommend Mobil 1. Why I have been using it for numerous years, and so have all my brothers and father, since the mid 80s and it has always worked great. Case in point my brother has an 88 Ponitac, you can pull the valve cover and the top of the head looks just as clean today as it did new, no build up sludge varnish etc. Synt. oil has been used in the aviation field for decades with great success, so I see how that translates to autos. Also, Synt oil has a higher break down rate than reg. oil so for me its the way to go.

Having said that I have also used reg. dino oil, but you gave two choices, I dont like Pennzoil, Id use Castrol...but you didnt ask about that.

[Dozer.]

I run Mobil 1. I beat the HELL out of my last truck (Durango). I never changed the oil religously. That truck now has 75,000 miles and runs great!

Spend the extra, your engine will like you better Synthetic has a detergent in there, which also helps over the long haul!
You ever hear when people run regular oil in their vehicle for a long period of time and then switch to synthetic having problems..... That is because of the detergent in the sythetic. Regular oil simply cannot keep the engine as clean as sythetic, so when you switch a high miledge vehicle over, all that junk starts to then loosen up, which causes issues

If you plan on keeping the vehicle, I would definitely suggest synthetic, especially since you are starting from a new engine.

[paroxysym]

ive been using quaker state oil... but ill be switching to mobil 1... i think quaker state is a culprit in my battle with my lifters...

[SurvCat]

I use Quaker State 4x4 & SUV oil....but only put about 8,000 miles on the jeep since I've owned it

[igofshn]

[QUOTE=jeepitup]Spend the extra, your engine will like you better Synthetic has a detergent in there, which also helps over the long haul!
You ever hear when people run regular oil in their vehicle for a long period of time and then switch to synthetic having problems..... That is because of the detergent in the sythetic. Regular oil simply cannot keep the engine as clean as sythetic, so when you switch a high miledge vehicle over, all that junk starts to then loosen up, which causes issues

QUOTE]
If you change your oil regularly, your engine will like you better. Regular dino oil has detergents also. Synthetic oil doesn't cause problems with higher mileage vehicles. Regular oil will keep the engine clean if you change it regularly.

[RUB1CON]

I have always run Mobil 1 for all 50,000 miles

[Dozer.]

Synthetic oil can cause problems to a higher miledge vehicle that has never had synthetic in it. Been there (unfortunitely, I found this out with an older car I bought years ago!) and seen how it will loosen up junk that led to troubles.

Synthetic will be better in the end, any way you cut it. If you were to do a study (as I'm sure they are out there) of which engine would be running stronger after a 100k miles of wear and tear (same factors of course), I would be willing to put some money on the results of the synthetic over time.
Otherwise, there would be no reason for synthetic (or the extra money that it costs).