Honestly the 4.0l is happy as long as theres oil in it, I've alway run whatever is on sale and ive seen personally 3 jeeps over 200K and one to 180k without issues. And an oil leak is one of the best things for a motor because then you constantly add fresh oil, lengthening the time between oil changes.

 

Pennzoil use to be a parafin (sp?) based oil. But in the early 2000's they went to a pure base.I still do not use Pennzoil because of the 'previous' base stock experience-I worked in a few machine shops in different states and have seen all kinds of things......Fords never liked pennzoil. It created massive sludge even w/ routine maintenance. I have seen engines with almost 200,000 that used synthetics since new and didnt need ANY machine work on the block or crank/rods. Here is some (actually ALOT) of reading regarding oils,viscosities,mineral vs synthetic...etc.
Good Reading!
http://search.yahoo.com/r/_ylt=A0oGd...=haas_articles

 

The minute you pour Pennzoil in your jeep it will fall apart, just like how anything with a Dana 35 will snap the rear axle after the first pot hole.


Check out Bobistheoilguy.com. Lots of good info on oil among other automotive topics. I hate when people state "facts" when they have no idea what they are talking about. Pennzoil had issues LONG ago, but is now one of the best oils you can buy. Mobil 1 actually shows more iron wear in the 4.0 UOAs (used oil analysis) than most other oils. The 4.0 isn't picky about oil. Just keep it full and change it often and you will be fine. I'd be more concerned with the body of the jeep rusting.

 

I use Pennzoil high mileage and my 4L runs good. I heard of all the myths and just read online about the different oils and from the info I was reading Pennzoil seems to be the best IMO. Just do sone research and you could come up with your own answer. I have used Pennzoil synthetic the wife's chevy 2.2L since the first oil change and now has 75000 miles on it and still running strong with no problems.

 

I had a 1969 Ford Bronco. Only ran Pennzoil 30W in it. After 97K miles, the valve covers were pulled. Mechanic asked me when the heads were rebuilt. I told him the last time the valve covers were off was when the 302 was built in the factory. Springs were bright red, there was no sludge buildup anywhere, everything was clean. Sold the Bronco with 119K miles on the odometer. Guy I sold it to continued feeding it Pennzoil.

I am not going by what a friend of a friend said, or what I read. My personal experience with Pennzoil is excellent. All lubricants must meet minimum standards. Choose the one you like, and very important, change it regularly.

 

I've never used Pennzoil, but my family and i have used Castrol 10w30 for as long as i can remember. None of our vehicles have ever had to have their engines rebuilt or replaced. '92 xj 180,000, '90 xj 180,000, '93zj 258,000, '94 chevy 1500 286,000, '79 z28 well over 200,000(odometer broke long time ago), 2007 chevy 3500 gas 316,000(sold), and 2010 chevy 3500 gas 99,000.

 

pennzoil gunks everything up. i dont use it in any of my vehicles.

 

 

Just change your oil. I run the best Mobile 1 but you don't have to run it. There are oils that are better then others but if you just change it you will be fine.

 

Oil is one of those things that is debated ad-nauseum, and that will continue till the end of time.

I have no issue with that, as this is a forum.

But man................it is overkill in my book.

 

I've used pennzoil platinum full synthetic for as long as I've had my jeep and have had no problems at all! I know some people don't like it but I would definitely recommend it

 

I've used Pennzoil in my 4.0 for the last 100,000+ miles. Just had the motor rebuilt due to a broken piston skirt at 263k, my builder said my motor was clean with no build-up. I asked him which oil he preferred, and he said he uses Pennzoil. That's good enough for me.

 

Go to Wal Mart, buy some Super Tech oil. Buy a good filter somewhere else. I use to be obsessed with oil, lol , not any more. Oh and for the OP my wife used penz in her liberty from day one. She liked the yellow containers.Had 143,00 miles with no problems. She changed it every 3,000 miles.

 

ROFL

 

According to our judicial system it is. Castrol got the meaning of synthetic oil dumbed down.