Another Oil Recommendation Thread (Jeep 4.0L)

[Katapl]

1. What kind of vehicle you have

I just purchased it today! It's a 1996 Jeep Cherokee with the 4.0L

2. What your owner's manual says

Beats me. I don't think I have one.

3. Where you live

Minnesota. Temp range is -25'ish F in the winter to 90'ish F in the summer. Winter is quickly approaching, and I want this all sorted before it gets too cold.

4. How you drive (easy? hard? fast? slow?)

I'm a pretty easy driver. People accelerate harder than I do all the time and I go easy on the throttle. However, I may be wheeling this thing a little bit and pushing it kind of hard.

5. What your daily drive is like (short trips? long trips? city? highway?)

About 50% of my driving is 1-2 mile trips. 25% is 2-6 mile trips, and the rest is wherever I need to go outside of the area.

6. Whether your car has any known problems

None I've found yet. Let's pray it says that way.

I prefer a store bought oil, and I don't think I have preferences between conventional or synthetic. Really, whatever BITOG thinks is better to suit me is what I'll get.

Also, I do not know the maintenance history of this Jeep. If someone can recommend me some tips, I'd like to flush the crankcase for peace of mind. What's the simplest and cheapest way to accomplish this? I mean, I don't even know where to begin. I normally would have thrown 1/3 Seafoam in and changed it a short while later, but I read here that Seafoam is not the safest thing to use in the crankcase. However, something about using MMO somehow? I'd also like to clean the combustion chamber and upper engine. Ideas on what to use?

 

[Cipriano]

I take care of a relatives 2001 Cherokee 4.0L. I recently switched to a HDEO and it loves it. Don't know how to describe it, just seems to run "tighter". I'm using Shell Rotella T 15W-40. For winter I'm gonna switch to Rotella T5 10W-30 which is a semi-synth. But then it gets much colder in MN so maybe Rotella T6 5W-40. Is it garaged at night? For cleaning I'd give it a bottle of MMO with the Rotella, run it for 1,000 and change it out.Then go 3-4K OCI after that. That's my two cents.

 

[Katapl]

It's not garaged at night. It's going to sit out in the elements. Is Rotella T6 5W-40 going to be usable when the cold hits here though?

So to properly use MMO, I'd just change the oil first, throw in a bottle and drive it 1k miles or so and then change the oil again?

 

[Cipriano]

Yep, that's what I would do with the MMO. That will give it a head start and then subsequent oil changes will have an easier job cleaning things out. Seafoam does have a reputation of being pretty harsh. This is funny you should ask about the Rotella standing up to outside temps. My relatives Cherokee is outside all the time and I was worried about the Rotella T5 being a little on the thick side for winter (can get to about -5f here). So just last night I ordered a Kat's oil pan heater for it. The 150 watt variety is just $19 on Amazon with free shipping. So I added a $6 DVD and got free shipping. Are you handy? Maybe an oil pan heater might be good for you even if you go with a 5W-30 SM oil.

 

[Katapl]

Ya, a block heater or oil pan heater doesn't sound too bad. I know my old man definitely runs one in his Ranger. I really haven't had a problem with starting any vehicle I've owned here yet.

A heater is definitely a good idea though. I think I just might get around to that before winter hits.

 

[Gary Allan]

If your 4.0 has no lifter ticks at this age, I'd say that it was well cared for. The bottom end is (just about) bulletproof and the valve train tends to be the first notable/audible victim of neglect. They're not particularly quiet to begin with.

If you want to do some investigating, test the timing chain slop by measuring the degrees of crank movement without the distributor rotor turning. That's about the only semi-internal item that may fatigue at ultra high mileage. Your rear main may seep

5w-30 is recommended for this engine. 10w-30 is preferred. It has been spec'd from 5w-20 through 20w-50 over its life span (4.2) depending on ambient temps.

You can use 5w-20 without issue, but I don't think I'd offroad with it if a bunch of wheel spinning is going to be involved. It really won't care too much either way otherwise. Go as heavy as you please at higher temps. Even with the lightest oil you can find OTC... under your normal driving you won't be on the visc chart when you turn the key off.

It's a very reliable engine. Everything is pretty simple. Not a whole lot to go wrong.

 

[Cipriano]

Okay, just checked my sisters 2001 manual. It says 10w-30 for above 0f, 5w-30 for below 0f. Can't say whether the 1996 manual says different but the 4.0L didn't change much during that time period. Maybe some others can offer advice on whether the T6 5w-40 would hold up in your winters. If so, you could stretch out your OCI's as it's a synth.

 

[Gary Allan]

Well, it shows 10w-30 (preferred) from 0F up and 5w-30 from 0C down..but that's close enough

 

[Cipriano]

Well, I'm cold at 0f or 0c. And my blood doesn't flow as easily. But I think that's because of all the red meat I eat. Would seafoam clear that stuff out?

 

[Katapl]

I've used 5w-30 through most winters, so no qualms about doing it again. I will also do 1000 miles on new oil with a quart of MMO. Does it matter what oil I choose (synthetic or conventional) when I do the 1000 miles on a quart of MMO?

Beyond that, if there's no problems using Rotella T6 5w-40 in this engine, then that's what I'm going to do when everything is sorted. I actually have Rotella T6 in my turbo Saab and it seems to be doing just fine.

 

[Cipriano]

Originally Posted By: Katapl
Does it matter what oil I choose (synthetic or conventional) when I do the 1000 miles on a quart of MMO?


I'd definitely use conventional. It would be a waste to use synth on a 1k cleanout.

 

[Katapl]

Being that the 4.0L takes 6 quarts as far as I know... I just use 5 quarts conventional and 1 quart of MMO? That seems simple enough. I'll head to AutoZone tomorrow and grab a quart of MMO and their current conventional special. I believe it's Mobil Clean 5000 and an STP filter for $13.

 

[demarpaint]

Originally Posted By: Katapl
I've used 5w-30 through most winters, so no qualms about doing it again. I will also do 1000 miles on new oil with a quart of MMO. Does it matter what oil I choose (synthetic or conventional) when I do the 1000 miles on a quart of MMO?

Beyond that, if there's no problems using Rotella T6 5w-40 in this engine, then that's what I'm going to do when everything is sorted. I actually have Rotella T6 in my turbo Saab and it seems to be doing just fine.


It doesn't matter what oil you add MMO to. Since this Jeep is new to you, I'd use 5W30 dino and do a 3000 mile OCI with the MMO in the oil. If you plan on doing 1000 miles with the qt of MMO I would wait till the last 1000 miles of the OCI. After that you can use either a 5W30 or a 0W30 oil.

 

[rslifkin]

The T6 should be fine in there. I ran it in my Mom's 99 Grand Cherokee 4.0 last winter, behaved and sounded fine at startup after sitting outside in 15*F weather.

4.0s aren't terribly picky, as long as the oil has enough ZDDP to protect the flat tappet cam. Keep in mind, they're kinda noisy engines, so a little lifter tick at times, particularly as the age, as well as mild piston slap (sounds almost diesel-like sometimes) is common, and normal, even in perfectly maintained examples. They run forever, just don't expect them to sound new forever.

 

[gomes512]

In my 4.0 I haven't noticed much difference between the use of PCMO and a HDEO according to my UOA's. These aren't exactly high-perf. flat tappet engines.

The trans always seems to be the most neglected part on these rigs. Although the 42re has a bad rep. it does last if you stay on top of fluid changes.

 

[Katapl]

Originally Posted By: gomes512
Although the 42re has a bad rep. it does last if you stay on top of fluid changes.


I got one with an AX-15!

 

[mechtech2]

I see storage outside and Minnesota winter!
So something with a 0 or 5 first number is wise. Full synthetics flow a bit better at low temps, too.
You #1 priority with winter approaching is cold start flow.

 

[dnastrau]

Originally Posted By: gomes512
In my 4.0 I haven't noticed much difference between the use of PCMO and a HDEO according to my UOA's. These aren't exactly high-perf. flat tappet engines.

The trans always seems to be the most neglected part on these rigs. Although the 42re has a bad rep. it does last if you stay on top of fluid changes.


The regular Cherokee has an Aisin-Warner automatic (bulletproof - uses Dexron fluid). If that is what you have, they are very tough.

The 4.0 Grand Cherokee (except for early '93) uses the 42re Mopar trans (Mopar ATF+4 fluid.) I have a 42re in a '96 Grand Cherokee with 178K on it and it has been fine. These are closely related to the old A904 Torqueflite transmission. A lot of the problems with the 42re are related to the governor pressure sensor and transducer that can go bad. These can both be replaced fairly easily.

 

[Katapl]

Well I'm driving around with 5 quarts of store-brand 10w-30 that was lying around and 1 quart of MMO. I will definitely be changing to Rotella T6 5w-40 before winter.

How many miles should I aim for with this 1 quart of MMO before I drain everything and change over to Rotella? Any need to change the filter mid-way through what I'm doing now? I thought I'd read somewhere...

 

[rslifkin]

I'd run it for between 500 - 1000 miles. The filter should be fine over that period. Of course, if the oil suddenly turns black and nasty looking one day, the filter may be filling up.