Hoenestly

As I look at this picture it makes me think "what makes a jeep run a very long time on the stock engine". I personally know this person, she beats it, by no means is the 400k mile jeep babied. Yet it runs true every day. But then I see some xj owners replacing engines at 200k.

My purpose for this post is to get a guide or general rule book for high mileage jeeps. The service log in the back of the owners manual only goes up to 120k miles. If any of you guys have high mileage jeeps and would like to share the maintenance/ long levity practices to keep them in good shape. That would be great!

(stuff like: 223xxx miles this went out and had to be fixed....etc). Just trying to get an idea of high mileage jeeps and the big things to look for and fix. Also maybe help anyone else!

fijicorey25

First and foremost is changing the oil. The more beating an engine takes, the more frequently you will need to change it. Use Shell Rotella (see writeup by Salad on this forum). Also use a quality filter such as Wix or Mopar.

Next is the rest of your fluids. Coolant, transmission/transfer case, power steering, diff fluid, brake fluid. These don't need to be changed nearly as much as the oil but they are wear items.

Next up is your accessory items like the fan, fan cluth, power steering pump, water pump, thermostat, alternator, serpentine belt, idle pulley etc. These are pretty much a repair on an as needed basis. That is, replace when you notice one of them start to go bad (you should notice).

Now all you have (at least engine related) is the electrical stuff such as all the sensors and the spark plugs/wires. Plugs and wires are something you should do with regularity. For the most part, just replace these as needed.


There are lots of people that just neglect to do routine maintenance on these. If you inherit a high mileage 4.0, it's tough to tell how thorough previous owners have been in taking care of their engines. The vast majority of people I know and have observed just know that D makes it go forward, the skinny pedal makes it go and the large pedal makes it stop. The best you can do is be vigilant about potential issue and to spend your $$$ wisely on your specific/unique issues

moparado

Did she buy that 422k+ mileage Jeep used?
Has the engine been replaced un-beknowst to her?

fijicorey25's advice is a good start. Do it and hope for the best.
I'll add, don't let 'seemingly' minor problems fester. Fix them as soon as they pop up.

But sometimes its just the toss of the dice on how long an engine lasts..babied or not?
Maybe the original engine was built on a Monday or by a new employee...who knows!

JSJJ388

My jeep has ~280xxx on it. When I got it it was already at 265xxx. All original motor and all gaskets and seals seemed to be original. The PO didnt take care of it for the year he owned it. Never changed the oil in 11,000 miles. It was as black and thin as it gets. I changed all the fluids (diff, oil, coolant, tranny, tcase, brakes, and power steering) and did a full tune up (plugs, wires, dizzy rotor and cap, brakes, and alighnment) and have been working out the issues as they pop up. It now runs like a top aside from some lifter noise.

I have been doing oil changes at ~5000 miles using castrol 15w 40 and wix filter. Just switched to Rotella T5 15 w40 and it is much better.


At ~273xxx I replaced TPS, IAC, CPS, and Oil pressure sensor.

At ~278xxx I replaced the rear main seal and oil pan gasket

fijicorey25

I have to address that I didn't put any time intervals in my first post. This is because those vary depending on your usage. Oil is really the only thing that's pretty constant. I change mine every 3 months/3,000 miles. I wouldn't go longer that 5 mo/5,000 miles. I change mine that frequently because Rotella T5 is cheap and goes on sale frequently.

extrashaky

The more I learn, the less convinced I am that Rotella holds any benefit for our engines. Although it has high zinc content, Rotella's zinc and detergent package (which washes away the zinc sacrificial layer) are formulated and balanced for long distance highway use at constant RPM, which is how diesels are usually used. In a daily driver with a gas motor used around town at various RPM and a more frequent heating/cooling cycle, the balance and zinc formula are all wrong. I think you're better off with a high zinc passenger vehicle oil like Mobil 1 High Mileage. You won't do any damage with the Rotella (at the proper weight), but if the point is to preserve the cam with the extra zinc, you're using the wrong thing.

Also, this fad of putting 10W-40 in your motors when you don't need it is kind of silly. The spec is for 10W-30. If your oil pressure is good, there's no reason to go to a heavier oil. If your motor is old and loose, 10W-40 makes sense to give a little boost to the oil pressure and keep it going another 100K miles. But people are putting 10W-40 into relatively tight motors with good oil pressure. I suspect some of them are doing more harm than good from the oil not flowing as well.

I had some idiot kid on one of the Facebook groups tell me that you were supposed to use Rotella 10W-40 because the 4.0L is really the same as a diesel, and that it was "Cummin's little brother." That's when I realized this nonsense has gone too far.

fijicorey25

Alright, so maybe I shouldn't have suggested a specific oil. This isn't about which oil to use, which there is plenty of debate on other threads. The point was to say that frequent oil changes will prolong the life of the engine. However, I do agree that using the correct weight could factor into engine wear.

Do some research on what oil suits your needs best, then use that oil and change frequently.

moparado

extrashaky,
here we go again with the best oil for these 4.0s.

I disagree with your analysis.
The 00 and 01 4.0 engines especially run hot, real hot. They need the little added viscosity when up to temp.
Most common automotive oils today have little to no zinc compounds in them. Blame that on the invention of the cat converter.

These 4.0 engines are of a decades old design back when most automotive oils contained zinc compounds. Where is Pennsoil Z7 today?

Little has changed with these engines over the years maybe carberated to fuel injection, ignition, etc. most or all of which do not rely on engine oil for longevity.

Rotella T5 or T6 15w-40 is my choice of Summer engine oil and 10w-30 for Winter all along with a good filter.

Hoenestly

she bought with 300k miles on it with stock engine. At first, it was going to be just a temp vehicle till she saved up to get a newer one, but it never broke or anything so she just kept it.

extrashaky

Nah, that doesn't make any sense. If 10W-30 weren't viscous enough, 1) AMC and then Chrysler wouldn't have specified it for this engine, and 2) the low viscosity would be reflected in low oil pressure readings. It's funny when people think they know better what this engine "needs" than the engineers who designed it and refined it over the course of decades.

Not true. The "high mileage" varieties usually have as much zinc as the regular oil did before the change in SAE standards. The new standard for the mainstream oil is 800 PPM of zinc. Mobil 1 used to be 1100 PPM, so they repackaged the 1100 PPM version as "High Mileage" and created a new 800 PPM oil for the regular class. Not only are you still getting the same amount of zinc, but it's the right formula for the zinc to be laid down under daily driver conditions, with the right detergent package to be effective under those conditions.

But hey, you're probably not doing any serious damage with your fad oil, so keep using it if you need to maintain your illusions.

Hoenestly

Guys....as long as the jeep is running properly does it really matter lol.

moparado

Engineers?
You mean the same ones who allegedly tested, specified and approved the 331 heads for mass production?
Ever hear of automotive recalls? TSBs? uSoft Updates?

I'm a retired electrical engineer myself where i've seen a lot of incompetent engineers over the years. Most F'ups were caught at design reviews while some slipped by and made it into production.
Also, years ago engineering test results requires no further testing more than you think. Seen that with my own eyes.

In the last 20 years or so a new management phrase popped up...that is: time to market!
Get the product on the shelves even with known bugs to be later fixed in the field hopefully by software updates or in extreme cases, returned to Customer Service for 'repair'.

I personally toured a major petroleum oil company's testing lab years ago.
I asked the technician how they tested their oils for engine wear, he said they tested with 'new' engines running continuously with no start up provisions.

Most XJs still running today have 200,000+ miles on their engines.
The 100k mile marker is likely where bearings, rings, etc. start to wear.
As further mileage piles up, the increased wear can reduce oil pressure little by little.

And with the 2000 and 2001 Xjs, those engines do run hot. I know i've got one. Takes only a fraction of time for the engine to come up to operating temp compared to all other vehicles i now own or have owned.

Far as the zinc thing, only going by articles i've read that stated zinc has either been significantly reduced or eliminated in modern automotive oils.
True or not? I don't know for sure, just basing that on articles i've read.
But i do know one thing for sure, Rotella does have zinc in it.

I will say this, when my crate engine was first installed, i did use Rotella 10w-30 as a 'break-in' oil for the first 20k miles.
I changed oil recently and it was Rotella 15w-40 for the Summer.

To each his own i guess.

extrashaky

Not really. As long as you change the oil regularly and use the right weight, it's fine. I just find it silly that people get all excited over Rotella for no legitimate reason and then run the wrong weight in their engines.

Yes, exactly those engineers who realized they had a problem with the 0331 after two years and moved production to a different foundry in Brazil. Yes, those same engineers who issue recalls and TSBs when a problem is discovered.

And yes, those same engineers who DIDN'T change the weight of the oil specified for the 4.0L after more than 20 years of production, because it was the right weight of oil. Those engineers.

You're arguing against your own position. They never had to "fix" the weight of the oil, because it wasn't a "known bug." This is just nonsense the Rotella fanboys have concocted to justify running diesel oil.

We have oil pressure gauges to know if that's happening. If the oil pressure is still good, the gauge is telling you that there's no reason to run the wrong weight of oil.

And yet that still doesn't require heavier oil than spec if the oil pressure is still good. Chrysler continued to use the coil rail 4.0L for ten years and still didn't change the weight specified for the motor.

kgm

Guys T6 comes in 5W30 now!!!! Woo!

Orlo

If that rig really has 400k on it, the owners probably ran it through all kinds of quick lube places several times a year just because they had to change the oil so often. That means that it's likely that 4.0 had every possible combination of oil and filter brands. And it made it to 422k. Geek on that!