Well this turned in to an oil thread pretty fast... I like the idea that the OP has for this thread so I will actually add something of value.

158,000 - Radiator started leaking
158,000 - Clutch was replaced. Still worked but was at the end of its life
158,000 - Replaced all engine seals. Has been leaking for a while so I will call this one 130,000
150,000 - I was told the passengers window motor died
150,000 - I was told the AC pump went out
150,000 - I was told the fuel pump went out

 

As i mentioned i KNOW Rotella has zinc which most automotive oils had back years ago when the 4.0 made its debut.

Yes, but after two full years of empirical field data and likely a bunch of warranty head replacements with you guessed it, 331 replacement heads.
Duhh!

I'll agree, the specified modern oil weight IMO is ok for these engines say under 100k miles, but does it have an appropriate amount of zinc to minimize wear up to 300k+ miles?

Do you know exactly how they determined to spec in 10w-30? I don't either.
Did they run test engines only to the equivalent of 50k miles where the power train warranty expires?
Did they run the test engine continuously or start/stop where appreciable engine wear can occur?
Did they temperature cycle the engine during their testing or just test at room temperature?
What kind of load stresses were placed on the test engine?
Did they run multiple tests over the years when automotive oils were under going continual formulation changes?
Did they rely on old test data from years ago when just about all oils contained zinc and maybe even a straight weight oil?

Heard this more times than i care to remember from management, "we've already got some old test data, no further $$ testing required"?
Or, again from upper management, "everyone else is doing it, just spec it in".
Testing is only as good as the Test Engineer who designs the test.

Did they run a MTTF analysis and run tests to verify over the span of the 4.0?
Did they run tests to 100k+ miles where oil pressure can begin to creep lower?
Or just where the power train warranty expires?
Diesel Schmiesel, who cares about the name.

Yep and mine told me my 300k mile motor's oil pressure was way lower than when the engine was new. I was using Quick oil change places up to about 200k miles where i started to notice a definite drop in oil pressure. Those places always use the mfg's recommended weight.
Thats when i started to change oil myself. Boosting the viscosity did increase the oil pressure at hot idle.
And as i mentioned earlier, my 2000 runs hot which can take a toll on oil.

Whats the big deal going from 10w-30 to 10w-40 or even 15w-40 for Summer driving. I really don't get it. Or is it a vendetta against Rotella?

What does a coil pack have to do with the weight of the oil?

 

At 165K I had to replace ball joints and bearings, wheel hubs and inner axle seals. At 167K I had to replace the AC tensioner pulley and belt to get the AC working again. Other than that just fluid changes so far.

 

I only have 154k miles on my XJ I bought three years ago. I have receipts from the PO that show maintenance and here is a list of the none scheduled repairs.

73k Replaced Distributer, Replaced rear axels, carrier & pinion bearings, rear axel bearings.The PO destroyed the rear end by putting his boat in the water and not changing the diff oil.

94k New master window switch

103k New oil pressure switch

104k New transmission mount, lift gate props

115k New DS window regulator, serpentine belt

120k New radiator, water pump, thermostat, hoses

123k New TPS, New turn signal flasher

127k New starter

I bought it with 128k

129k repaired broken wire to center high brake light, New transmission mount. Repair fog lamp switch. New Front speakers.

130k New valve cover gasket

144k New cooling fan clutch

146k New alternator

148k New catalytic converter

150k New windshield

Currently I have 154k and a few issues that need to be addressed: oil filter adapter and oil pan have drips. Power lock actuator on PS rear door is not working. Also I'm sagging about an inch on the rear leafs. Other than that I'm golden...I don't know if it will be the last vehicle I own but if I can get another 10 years and 100,000 miles out of it I will be happy.

And since everybody is so interested in oil it has pretty much only had Pennzoil yellow bottle its whole life. 10w30 until I got and I ran two oil changes of Rotella T3 15w40 and now I'm back to the yellow bottle 5w30.

 

Dad's old ZJ 4.0
Hit 420k+ miles before he cash for clunkered it, piston rings were pretty gone at that point, possible head gasket failure but I can't remember it failing to start EVER.





Changed the spark plugs like twice ever. Don't think we ever even changed the front diff fluid or transfer case fluid. General maintenance as parts failed (water pump, HVAC, went through 2 or 3 transmissions in it's life though)

Probably a unicorn but my 4.0 is at 260k and still going strong (though I take WAY better care of it, but beat on it more. Probably evens out. Or luck of the draw. Who the hell knows....)

 

What do you mean: "just switched to Rotella T5 15w40 and it is much better" ?

Better in what way?

PHM
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It means that he read all the Rotella fanboy comments on this forum and is imagining all the miracles that are occurring in his jeep from a freaking motor oil.

 

What I mean is that I had been running Castrol high mileage 15w40 because the jeep has a lot of miles and I have always ran Castrol oil in my stuff. I was told that our 4.0s like the T5 oil so since it was on sale, I decided to try it when I replaced my rear main seal. The engine cranks and runs smoother (could be rear main as well), it builds oil pressure much quicker, the hot idle and driving pressures are a little bit better, and the most noticeable thing, my lifter noise is much more quiet. The jeep sounded like a diesel before hand, now you just hear a light ticking.

 

Try again, it means that I tried it and it helped. If you dont want to run it, dont run it! Ive never been a die hard for any particular brand. I just run what works best for me. until now, I ran castrol 15w40, I thought id try the T5 and see if it made a difference. It did. Is it because its T5 or is it because its synthetic? I dont really know. I may try running another synthetic and see if it has the same qualities. Im not claiming any miracles lol. Nothing I have said is crazy or un heard of. It helped my oil pressure and made my lifters a little more quiet. Whats so outlandish about that?

 

That's because Rotella has unicorn semen in it. Like a billion zincs yo.

 

Damn who has to milk those unicorns?

 

Thanks for expanding your comment for me - I was just curious what "better" mean in this context.

Since we are talking about engine oils: I have A Story. <g>

On February 14, 2001 I bought a new Triumph Bonneville and it really has been a Sweetheart. <g> It came with Mobil 1 in it and so that's what I always used - about every 5000. It's a great bike, I still have it, and I have hammered it somewhat mercilessly. Towed a heavy trailer all over the place, shifted at the redline, often ran it as fast as it will go (at 105 - the rev limiter kicks in), etc. At about 35,000 miles it got knocked over, the shift lever broke off, and the end of the cross-shaft splines got damaged.

I had to pull the engine side covers to replace the shifter-shaft and thought: May as well replace the well abused clutch while my hands are dirty. When the parts came in I pulled the engine apart and then noticed that the factory gave go / no-go specs for the clutch plates. That got me curious about just how bad the well hammered clutch actually was.

Oh wait; the first thing that caught my eye was the inside of the engine - it looked literally New inside. I have had A Lot of used engines apart and I have never seen anything like it in a used engine. Absolutely Spotless.

So I mike the clutch plates and find them Exactly the same thickness as the new plates. 35,000 Hard miles and zero wear. That was some years ago and the new clutch parts are Still sitting on a shelf in my basement. <g>

My father worked for Mobil Oil for 40 years and I feel like I grew up in a refinery. <g> And I remember when the Mobil 1 was being developed and tested (it was just called The Synthetic Oil Project at the time) and how my father and his friends were amazed by the test labs results. Zillions of engine hours with no wear and etc.

Now my father would never actually BUY any Mobil 1 oil when it came out - too damned expensive he said. <g> And I didn't either - until I saw my Bonneville engine and clutch.

I have a Corolla (21K) and a Tacoma (170K) that have always had Mobil 1 but with the Jeep I have been thinking: already 250K miles on it - does it Really need Mobil 1? <g>

That's what made me curious about your Rotella Experience. <g>


PHM
--------

 

I have always heard that mobil 1 is great oil. I have run it a couple times in my dirtbike and once in my dodge just because it was on sale. Never gave any issues but i used conventional. I am impressed with the T5, but I am not sure if it is the T5 or just that its synthetic.

 

Yeah, i'm one!

 

Yea Im not really a fanboy of anything. I stick to what I know works well unless someone shows good evidence that there is a better option within my budget. Just so happens, I was convinced to switch to T5, and it did help.