Ok, I'm trying really damn hard here to be nice and even took the time to sift through this whole damn thread to eliminate any unwarranted BS, so here's the deal...If you don't like it, DON'T USE IT! Now is that soo hard of a concept?! I don't think so.

Secondly, IF you don't like something that others do, that goes for oils, lift kits, tires or whatever, don't flat out bash. You need to state why and come with evidence of why. If not it comes off as this, "Well Billy, I see you lifted your XJ but didn't buy the brand I like and bought all terrain tires instead of crawlers. You really screwed that Jeep up and need to sell it."

So last warning. Being respectful to others here really isn't up for debate either.

 

It's a shame that such a simple fix to a design flaw gives the whole thing a bad reputation... when in reality, if they had only modified that part, they would've had a winner

 

Yep... We raced a few after this fix and they were strong and hard to beat.

 

Yea it doesn't have to be Rotella, I run 15w40 Castrol diesel oil instead. I have a bunch of it because I stocked up on it when Wal-Mart had it on sale for $5 a gallon.

 

Didn't know Castrol had a diesel specific oil, or at least I have not seen that stuff down here. Got a pic of the jug? The Walmarts here only sell the Delco, Rotella and Quaker State diesel blends.

 

 

10-roger.

Ha! Learn something new every day!

 

That stuff is junk. Evidence; it doesn't say Rotella on the jug. I'll bet your poor 4.0 doesn't even make half million miles running that garbage which will prove that you're totally dumb for using it. Please tell me I don't need to insert a smiley, that would totally ruin it.

Been so long since I saw a Powerstroke referred to as a T444E. My van has it's older IDI brother. Gutless wonder, but it burns everything I pour down its throat. Mechanical Diesel engine, the original flex fuel.

 

I didn't read all 500,000 replies, but I will ask this: If the 4.0 engine needs 10w30 oil, and it is as bulletproof as everyone says, then 10w30 Rotella should work just fine, yes?. If someone should use the 15w40 in the dead of winter, it might cause some issues, but in the heat of summer, I assume it will be just fine.

YMMV
Don't shoot the messenger.

KenR

 

Yes.

 

A buddy of mine had one of those old idi 7.3s, not much power but it they will run forever, and when you got on it it sounded more like big block gas engine than a diesel.
I have no issues running 15w40 in 20 degree weather, and yes 10w30 Rotella would be fine to use. The 4.0 originally specd as high as 20w50, 10w30 is the lightest I would run in a 4.0.

 

I find it very funny to hear all this obsession over oil. The 4.0 has survived on every type of oil thrown at it. The reason for thinner oil in winter is for easier starting. Oil pressure will start to build as soon as engine starts. The rockers are SQUIRT lubricated and it may take several MINUTES for oil to reach them regardless of oil weight but so what? There is enough residual oil to lubricate adequately until oil flow is established. Even after the engine has sat for a long time all moving parts are coated with a film of oil.

 

oil is a HUGE deal on this forum. Every oil that someone uses is the best dontchaknow?? C'mon man where you been?

 

FWIW, back in the 1980s and early 1990s I worked in the computer department of a major oil company's R&D lab and had the opportunity to work with their lubrication engineers. Their opinion at the time was that if you changed your oil and filter every 3K miles it didn't matter what oil you used as long as it wasn't some unknown cut-rate garbage. (The exception being turbocharged engines, where synthetics were recommended due to their superior heat resistance. Also synthetics were recommended if you wanted longer drain intervals.) A number of different makers' cars using a lot of different oils were stress-tested, then torn down and analyzed. I don't specifically remember any XJ 4.0s but given the Jeep's popularity I expect there were some.

Of course back then we didn't have the low ZDDP problem to deal with, but that seems to be an issue mainly when in breaking in new cams or with high-performance engines using extra-stiff valve springs. (I do use Rotella T6 in my own XJ mainly since so many here recommended it but I'm sure any quality oil would do just as well.)

So pay your money for what you like, say a voodoo prayer over it, and carry on.

 

Agreed. I've read about several quite controlled studies over time regarding oil as well.
One was a study of a set of NYC taxi cabs. They broke the motors all the way down, measured the current condition of all of the parts, from the crank to the cam and everything in-between. Then put them back together. Then using the same quality oil, then half the cars they broke back down after 3000 miles exactly. And remeasured...the other half they broke down at 5000 miles and measured everything again too.
And what they found... there was no more wear on the cars that went 5000 miles than those that went 3000 miles. And we all know that NYC taxi cabs are probably among some of the hardest used cars around in those conditions. I'd say that's a pretty controlled real world test.