4.0's favorite oil? (and change interval)

[brucecooner]

My recently bought MJ came with a pan full of fresh clear oil (all the fluids I've seen look fresh), but I forgot to ask the seller what he had put in it.  They did say they put 5W30 in it, but that's all I know.

 

I'd like to change it soon anyway, and put it on a schedule suited to a 4.0 close to 200K.

What brand/formula do guys here roll with that's made their motors happy?
Is a "high mileage" formula called for?

If I switch to a full synthetic will it suddenly clean up a bunch of gunk and start seeping?

 

What interval seems to suit them?

I've heard conflicting things about time versus mileage.  When I got the reman motor in my Ranger the tech said change it every 5K OR 5 months, whichever came first.  That struck me as odd but maybe the extreme Arizona summers will break down oil even sitting in the pan?

I work from home, don't commute, and have been putting just 2 to 4 thousand a year on my previous truck, but going by miles and changing the oil yearly would just feel weird, so I have been keeping the five month schedule on it.

 

[87MJTIM]

The owners manual calls for 10W30. I don’t remember the intervals. I’ve done every 5000 miles or 6 months. 

[89 MJ]

The owners manual for a 90 with a 4.0 says 7,500 miles between changes. I give mine 3,000 between changes. 

[JimiGibbs]

I use a high mileage synthetic (Mobil 1). Not sure if it is worth it but with 150K miles it can't hurt.......

[ghetdjc320]

As said above, the weight is 10w30. It’s good to keep in mind that these engines run a flat tapper cam so an oil with added zinc or a separate bottle of zinc additive is a good idea. Vr1 racing oil is what I used to run as it has good levels of zinc. But there are tons of options. 

[watchamakalit]

Rotella t4. Got the extra vitimins and minerals built right in.

[75sv1]

I use Rotella too. I used T4 before, and a NAPA Silver or Gold filter. Presently, I use T6 and a NAPA Gold. I do prefer to use the NAPA Platinum filter with synthetics. With T4, I'd run at least 4K OCI.  With T6, at least 8K OCI. I change yearly, with synthetic oils. The Rotella has around 1200 ppm Zinc. So, good for the flat tappets. I have put synthetics in high mileage engines. My 2000 XJ, I bought it with 260,000. It does leak a bit at the rear main seal. Or Possibly, and hopefully, at the filter attachment. I have been using Rotella in the Jeeps since 2002. Rotella does make a 10W-40 T4. It is Diesel rated. I did use it in my XJs, year round and in my MB 240D for the colder months. I use T6 now. 

[cruiser54]

T4 with Wix or NAPA filters for the win. Silver is good for 3500 mile intervals, Gold for 7,500 which is factory interval except for severe service like taxi, postal delivery etc. 

[dasbulliwagen]

The diesel rated oils. I'm in the southeast, so I run 15w40 year round, and I don't do a lot of milage so I change once a year. On a 200,000 plus miles 2.5L, with a Mopar filter. 

[brucecooner]

Thanks for all the info everyone! 

I'm still in the data compilation phase.  There's a spreadsheet involved.

 

I'm not too worried about it currently having fresh 5W30 as opposed to 10W30.

I guess it's just giving me some low temp protection I don't need here in the desert.

The guy who sold it to me was an older guy with a shop who buys and sells a lot of XJ's, and had older iron on the lift when I'd visit (including a super nice J80 Cruiser) I feel like there's a decent chance he knew what he was doing when he changed the oil in mine.

 

That said I do plan to switch for 6 quarts of Rotella T4 pretty soon.

Of course there's a lot of threads out there where guys claim after a certain mileage the parts are heat worked or have a permanent coating or something and the zinc is unnecessary and whatever oil is fine.

My preference is to go with factory spec though. 

 

My plan is a six month schedule, or every 3000 miles whichever comes first.

 

I'm not sure on the filter, yet.

I've still gotta look up the number on the Mopar filter.

In my Ranger I've been running Mobil 1 oil and filters for decades now, so they're familiar to me.

But there might not be much difference with any high quality filter though, particularly on a frequent change schedule, but I'm open to anecdotes.

 

I seem to remember reading that some flavors of AMC used an oil filter adapter?

Is that something I have to consider?

 

Also, should I worry about draining one weight for another, or pouring in a different oil right after draining whatever was in it before?

I know the SAE and manufacturers are particular about ensuring oils can mix without issues, but it's something I've only done a very few times.

 

 

 

 

[cruiser54]

Ever see this from the owner's manual?

 

Jeep Engine Oil Viscosity

This was taken from pages 82 and 83 of the 1989 Chrysler/Jeep owners manual.

Selecting Engine Oil Viscosity

When changing or adding engine oil select the proper grade by using the chart on the following page. Select the grade that corresponds to the ambient temperature range you expect to encounter before your next oil change.

30*F to 100*F+    20W-40 or 20W-50
0*F to 100*F+        10W-30 or 10W-40
-20*F to 60*F        5W-30
 

[brucecooner]

3 hours ago, cruiser54 said:

Ever see this from the owner's manual?

 

Jeep Engine Oil Viscosity

This was taken from pages 82 and 83 of the 1989 Chrysler/Jeep owners manual.

Selecting Engine Oil Viscosity

When changing or adding engine oil select the proper grade by using the chart on the following page. Select the grade that corresponds to the ambient temperature range you expect to encounter before your next oil change.

30*F to 100*F+    20W-40 or 20W-50
0*F to 100*F+        10W-30 or 10W-40
-20*F to 60*F        5W-30
 

No sir, mine didn't come with an owner's manual.

I really should download one and save you guys all the questions.

 

It's interesting that the second spec goes to 100F. 

We can get strings of summer days above 110F here in Phoenix, which makes me wonder if I should aim for 10W-40.

(my understanding is that the second number represents high temperature protection, with higher numbers indicating stability at higher temperatures)

My hunch is that 10W-30 would work fine for my application, and I'm just over-analyzing everything.  If 30 weight oil meant death to cars in Phoenix I'd probably have heard about it by now.

 

 

[cruiser54]

Agreed.

 

I run 15-40 in everything I own up here in Prescott. 

[big66440]

I use Mobil 1 or Napa full synthetic ( made by Valvoline) 10W-30 and the Napa gold oil filter # 1773, and do my oil changes every 6,000 to 6,500 miles.

[Jeeper1093]

Castrol with a quart of Lucas high mileage and you're good for 5k

[brucecooner]

*clambers out of muddy pit wearing snorkel, collapses at edge of pit*

 

Wow, a LOT of digital ink has been spilled on this topic. 

Not just regarding the best oil for an old AMC 4.0L, but on motor oil in general, for every engine.

Literally. Millions. Of threads.

 

I've never really known anything about oil except what kind tastes best on a salad.

But now I own this really old truck so I had to dive in.

Even after a lot of hunting and reading I still can't say I know much, BUT I learned a little...

 

-The first number is cold weather performance of an oil. The farther north you live, the lower of a number you'll want.

-The second number is the thickness of the oil when hot in an operating engine. Check your owner's manual for this number.

-Jeep owners go looking for diesel oil because by classifying their oil as diesel rated first, and passenger car rated second, the oil makers have more leeway on the ingredients they can add and thus make oils more suited for older engines.

 

In all my searching I did find a couple of more helpful than usual sources.

 

Most anyone who's changed the oil in an internal combustion engine who has an internet connection knows that Bob truly IS the oil guy, and as you'd expect there's a pretty good "Oil 101" intro over there: https://bobistheoilguy.com/motor-oil-101/

 

More than a few folks here have probably read this one, so sorry to link to a near decade old thread, but salad's epic writeup over at CherokeeForum is helpful for unraveling what matters in an oil, and why.

https://www.cherokeeforum.com/f2/rotella-worlds-first-ever-combined-hair-oil-foot-ointment-salad-dressing-188168/?ispreloading=1

There is also a very informative chart of oil specs by brand in that thread that's worth the price of admission.

My super quick take on some of the ingredients...

Zinc and phosphorous (which usually come packaged in a compound abbreviated as ZDDP) are seemingly necessary anti-wear additives in flat tappet engines, and are decent anti-wear additives in general no matter the engine they're in.

Unfortunately phosphorous going out the exhaust over time destroys catalytic converters, but at spec-ish concentrations in a decently sealed engine it takes a long time.

There are modern anti-wear additives, most commonly molybdenum and boron, that are useful in all engines while being friendlier to cats and are thus more popular in modern cars. (I wasn't able to tell if moly/boron can fully replace the Zn/P combo, I'm guessing not).

Calcium cleans the engine, and Magnesium ensures the gunk stays in the oil without just re-depositing somewhere else.

Unfortunately calcium breaks down phosphorous. So your cleaning agent is working against your security agent.

 

Anyone who's read any oil thread knows that just about every point made in any given thread is debated there or elsewhere.

Some will say that in time, the parts in an old 4.0 are heat worked to the point that anti-wear additives aren't all that necessary, or the ZDDP concentration doesn't need to be nearly as high, etc. Some guys will swear by a single weight oil they've run for 18 years with no issues, etc.

 

All I can say I've really learned is that oil is a balancing act. You might gain something (better engine protection) but have to give up something else (the cat, eventually).

 

Anyway, salad produces a great big useful table detailing the specifics of many popular brands of oil, and summarizes his findings thus:

 

"For the Jeep 4.0L, Shell Rotella T6 is the most ideal oil to run. It provides the best balance of engine wear protection versus fuel economy, and is the best suited to provide the most reliable performance in all situations."

 

Then later he says that due to his research findings, he's going to switch to another brand that offers similar performance at a cheaper price point.

Which made me laugh, and I think drives home the point that you just have to get enough information to make yourself comfortable with a choice, grit your teeth, and follow through.

 

For me, after all that reading...

 

The first number....

Either 5 or 10 for the cold performance seems fine.

I live in the desert and the coldest morning in the frigid depths of a Phoenix winter won't be anywhere near zero on the mercury.

 

The second number...

The excerpts from the manual I've seen (see cruiser's quote above) say that you can run 30 or 40 weight.

But my engine has a couple of qualities that would make me probably lean toward the heavier weight.

 

It has almost 200 thousand miles, and quite possibly enough wear to warrant the thicker oil. (hey, even the venerable 4.0s do age)

It seems to have a nice rich leak from the rear main (I need to crawl under and make sure it's not the oil filter, Jeep ownership!)

I'm not naive enough to think a higher weight of oil will magically seal it, but maybe it will help? (hope springs eternal, Jeep ownership!)

 

So based on everything I've read I finally see why I feel confident going for the Rotella T6 5W40.

 

For sure though, I will run it for 3k, and have it analyzed to get a peek inside.

 

 

 

[brucecooner]

and thanks everybody for your input. 

 

It looks like my first choice is sold out everywhere, oy. 

Time to go snoop through the big oil chart....

 

[scguy]

56 minutes ago, brucecooner said:

and thanks everybody for your input. 

 

It looks like my first choice is sold out everywhere, oy. 

Time to go snoop through the big oil chart....

 

T4? The shop I work at is out of Rotella, no suppliers have it in stock, we've switched to Delvac for the time being. 

[brucecooner]

On 4/25/2022 at 5:33 AM, cruiser54 said:

T4 with Wix or NAPA filters for the win. Silver is good for 3500 mile intervals, Gold for 7,500 which is factory interval except for severe service like taxi, postal delivery etc. 

Back to this ancient topic.

Things have been busy, I'm still on the hunt for an oil.

 

All the T4 I see is diesel rated, and this is a point I haven't seen explicitly clarified.

People are putting "diesel oil" in their 4.0's?

Like, oil for diesels...

https://rotella.shell.com/en_us/products/triple-protection-motor-oil/rotella-triple-protection.html#iframe=L3NvcHVzL3JvdGVsbGEvbmV3c2xldHRlci9lbl91cw

It says on the bottle, "for diesels".

 

I see threads out there where random poster says he's running diesel oil, another guy says that bad, the mystery goes on.

I can imagine there's no difference between the base stock of oil in gas and diesel lubricants, and the differences are probably all in the additives.

Still, this seems odd to use a product not labelled for my intended use.

[75sv1]

Diesel 'rated' oils keep the soot in suspension, so it does not wear the bearings, etc. It will not harm a gas engine. I use the T4 and T6 Rotellas, mainly for the extra zinc. I'd run 4K to 5K on the T4, and 8K on the T6. The Delvac and Delo are good choices too. I did see some T4 at a NAPA last week. It was $24/gal. Ouch. It was gone a few days latter.

       

[cruiser54]

T4 for the win.

[JMO413]

6 hours ago, cruiser54 said:

T4 for the win.

Agreed.

[knever3]

I run Joe Gibbs HR2 10w-30 Racing oil in my stroker because of the zinc content, with a quality oil filter as well.

[gogmorgo]

Primary argument for diesel oils is they contain higher ZDDP levels (i.e. zinc), similar to what oil formulations from the early ‘90’s contained. Primary argument against diesel oil is the ZDDP content was found to shorten the life of a catalytic converter, hence modern gasoline oils having lower levels. But yes, diesel oils also have higher detergent levels which will keep the inside of the engine cleaner.

My work fleet runs 5w40 diesel oil in everything, regardless of manufacturer ratings, and the only engine we’ve lost prematurely was one that the guy driving would refuse to give up the truck during the day to have the oil changed so it was regularly seeing double the recommended interval. And it was still squeaky clean inside when we pulled the pan, it just wiped out all the main and rod bearings. 
 

The other typical recommendation from the industry is to pick one oil and stick with it instead of changing oils all the time on the grounds that the additive packages between differing oils might not get along super nicely. 

[brucecooner]

On 7/29/2022 at 7:12 PM, gogmorgo said:

Primary argument for diesel oils is they contain higher ZDDP levels (i.e. zinc), similar to what oil formulations from the early ‘90’s contained. Primary argument against diesel oil is the ZDDP content was found to shorten the life of a catalytic converter, hence modern gasoline oils having lower levels. But yes, diesel oils also have higher detergent levels which will keep the inside of the engine cleaner.

My work fleet runs 5w40 diesel oil in everything, regardless of manufacturer ratings, and the only engine we’ve lost prematurely was one that the guy driving would refuse to give up the truck during the day to have the oil changed so it was regularly seeing double the recommended interval. And it was still squeaky clean inside when we pulled the pan, it just wiped out all the main and rod bearings. 
 

The counterpoints I've read to using diesel oil is that diesel oil additives are geared toward mitigating the different combustion byproducts that diesels produce (soot I think), versus gasoline combustion.

But I've never found a solid read on how, exactly, the additive packages differ between diesel and gas oils.  My impression is that the additives they use come from a small common set, but the ratios differ based on the needs of the engine.

I think I remember reading that calcium (I think it was Ca), one of the commonly used detergent (cleaning) additives, breaks down ZDDP, so the two additives are somewhat at odds (wear protection versus cleaning).

 

 

On 7/29/2022 at 7:12 PM, gogmorgo said:

The other typical recommendation from the industry is to pick one oil and stick with it instead of changing oils all the time on the grounds that the additive packages between differing oils might not get along super nicely. 

I've heard the same thing from some sources. My suspicion is that any of the oil manufacturers are careful to make sure their formulations mix with existing oils, or else they'd all be sued into oblivion if their oils started eating engines when mixed with some other oil.

That said, I'm a guy who likes consistency, and I've only put Mobil 1 in my Ranger for well over a decade now. I hope to settle on a single oil for the Jeep as well.

 

Add to all of this that a lot of these threads are a decade old, and technology marches on.

 

There's apparently been some recent changes to the exemptions for diesel oil additives when rating them, but only if you want to also rate your oil SP.

https://www.fuelsandlubes.com/fli-article/exemption-phosphorus-limits-longer-apply-2020/

Shell apparently limits their multi-vehicle blend to 800ppm of zinc.  I don't know if this applies to the SN rated (an older standard) multi-vehicle blend as well though.

But I'm guessing the Rotella that's always been high in ZDDP will remain so, knowing that so many operators have come to rely on it.

 

And then there's rat540, who has done a lot of testing and says all sorts of contrary-to-conventional-thought things in his blog.

https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/

He says zinc isn't needed for wear protection, that the physical properties of the base oil are mostly what matters for keeping metal parts separated.

 

I'm wondering if there aren't just modern replacements for ZDDP in oil, that lets it protect from wear while not killing catalytic converters.  I believe molybdenum and boron serve this purpose, but I haven't seen anything on whether or not they're suitable replacements for ZDDP.

 

I can get Rotella T6, but full synthetic is overkill for my application, light duty, and I don't even put 4K on a vehicle in a year. I change the Ranger twice a year and an oil change rarely gets past 2K (but I'm okay with it).

Synthetic blend might even be overkill, but I'm thinking I'll look up some T4 or T5.