Jeep 4.0L 214k mi; VR1 mix at 3k mi

[MechEng13]

Jeep 4.0L with 214,000 miles
3,000mi OCI
3qrts VR1 10W30 + 3qrts VR1 20W50
Mopar M090 Filter
ALS Tribology

I bought this Jeep last September. It has pretty severe piston slap on cold start, to the point that it sounds like a diesel engine until it warms up. After bore scoping each cylinder and checking the bottom end when replacing the rear-main seal, it appears to be completely original (original pistons and cam at least). I planned on rebuilding the motor over the winter, but this analysis might have changed my mind. The piston slap bugs me, but the engine does not burn a drop of oil and runs like a Swiss watch once warm.

As a comparison, I have another 4.0L motor with 135k miles that was rebuilt at some point in its life. That motor showed around 30ppm of Iron and about 5ppm of aluminum. From what I have read, 30-50ppm Iron is pretty standard for the 4.0L.

Photo of the worst cylinder wall. Consistent wear for 214k miles!

 

[fantastic]

5 PPM/1k Fe is at the higher end of "acceptable" IMO. Not bad though & the bores do look really good for the mileage. The knock could be connecting rod wear though which would require a tear down to inspect (unless can access via oil pan). Si is very high so please go inspect your intake filter & plumbing. Viscosity of this "15w-40" mix is no longer a 40 grade but more than adequate for this engine.

This is an older VOA but it only shows 7 ppm Si.
https://bobistheoilguy.com/forums/threads/voa-valvoline-vr1-20w50.254289/

 

[burbguy82]

Silicon would suggest air filtering is an issue.

It looks like you have a stuck ring.

 

[Gene K]

It looks like you have a stuck ring.

A stuck ring without oil consumption?

 

[burbguy82]

sure

A stuck ring without oil consumption

How else does one part of the cylinder wear like that?

 

[burbguy82]

sure


How else does one part of the cylinder wear like that?

I would ditch the VR1 mix for now, and run a higher detergent oil than SP. It might help.

Evidently, VR1 is of an "SP compliant" (for lack of the ability to explain it better) formulation, with lower detergents, which evidently adds to the anti wear characteristics, but not good for the "cleaning of existing" conditions. I am not an oil expert, but this is my base line understanding.

I would try

https://www.amsoil.com/p/amsoil-sig...thetic-max-duty-diesel-oil-deo/?code=DEO1G-EA

or

https://www.amsoil.com/p/amsoil-premium-protection-10w-40-100-synthetic-motor-oil-amo/?code=AMO1G-EA

or

https://www.amsoil.com/p/amsoil-premium-protection-10w-40-100-synthetic-motor-oil-amo/?code=AMO1G-EA

of course it would not fix a mechanical wear issue, but they might unstick a ring. I have had that happen on my 4.0 jeep.

 

[KCJeep]

That is low iron for a 4.0 even at 3k.

 

[We're Metals]

VR1 has a solid add pack if you need Zinc. Very nice.

 

[Gene K]

sure


How else does one part of the cylinder wear like that?

Looks just like piston slap wear on a GM LS V8. They have corresponding wear on the piston skirt.

 

[FusilliJerry]

Later Jeep 4.0’s have issues with cracked piston skirts causing this noise caused by pinging owing to overheating. With that wear shown you should drop the oil pan to see if there’s pieces of skirt in there. Mine didn’t so I went another 10k before rebuilding but all 6 pistons were in fact cracked. Had the same exact noise that lessens when warmed. More than likely with the wear shown (worse than any I found in my bores), one of your compression rings is mechanically stuck by the piston’s ring land squishing it in place.

It needs new pistons (all 6; I guarantee more than one has cracks) but until then as insurance I’d be running 93 octane to prevent any preignition grenading a dead hole into the piston. Luckily, anecdotal evidence across the internet suggests they can go a long time with cracked skirts though bore wear will eventually worsen to the point of needing bored out.

The UOA is appreciated; I just did an in-frame rebuild and after a few close interval changes I’m running a similar mix with 2qt 10w30 and 4qt 20w50 VR1 (Philadelphia summers are HOT) and it runs smooth as a baby’s bottom. Good to know it gives good wear figures.

 

[Chris142]

There is a guy on YouTube goes by dex xj or something similar. He can replace all 6 pistons and have it back together by noon.

 

[FusilliJerry]

There is a guy on YouTube goes by dex xj or something similar. He can replace all 6 pistons and have it back together by noon.

Dexjs. He doesn’t do work for the public (I’d asked) but he does do a core return service putting new pistons on core connecting rods. It’s the only reason I actually went through with my DIY in frame rebuild. However it seems lately he is running into sourcing issues for rod cores and is frequently out of stock. I sent mine back so don’t blame me.

His videos are valuable and entertaining if a bit sloppy in certain respects, but he is a one man band after all.

He’s got a website; can be easily found googling his YouTube name.

The shame of yours having been rebuilt (so was mine) is that it’s not uncommon to reuse pistons but it’s not commonly known the stock pistons are weak. If you do it, you may as well also get a later TUPY or Clearwater head as 99-01 0331 heads are prone to cracking allowing coolant to weep into the valvetrain area.

 

[FusilliJerry]

I would ditch the VR1 mix for now, and run a higher detergent oil than SP. It might help.

Evidently, VR1 is of an "SP compliant" (for lack of the ability to explain it better) formulation, with lower detergents, which evidently adds to the anti wear characteristics, but not good for the "cleaning of existing" conditions. I am not an oil expert, but this is my base line understanding.

I would try

https://www.amsoil.com/p/amsoil-sig...thetic-max-duty-diesel-oil-deo/?code=DEO1G-EA

or

https://www.amsoil.com/p/amsoil-premium-protection-10w-40-100-synthetic-motor-oil-amo/?code=AMO1G-EA

or

https://www.amsoil.com/p/amsoil-premium-protection-10w-40-100-synthetic-motor-oil-amo/?code=AMO1G-EA

of course it would not fix a mechanical wear issue, but they might unstick a ring. I have had that happen on my 4.0 jeep.

Disagree in that apparently Valvoline using an otherwise SP add pack that lowers calcium helps Zinc’s effectiveness. I’m citing a Motor Oil Geek video as my source though he cites SAE/API as the basis for the change to SP and IIRC shows snapshots of their white papers which is good enough for me.

This is in fact low iron for a 4.0 so if it ain’t broke don’t fix it. I found this thread looking for exactly such a UOA and will continue using VR1 accordingly.

As for the ring, again I’d bet it’s stuck mechanically if at all.

 

[burbguy82]

Disagree in that apparently Valvoline using an otherwise SP add pack that lowers calcium helps Zinc’s effectiveness. I’m citing a Motor Oil Geek video as my source though he cites SAE/API as the basis for the change to SP and IIRC shows snapshots of their white papers which is good enough for me.

This is in fact low iron for a 4.0 so if it ain’t broke don’t fix it. I found this thread looking for exactly such a UOA and will continue using VR1 accordingly.

As for the ring, again I’d bet it’s stuck mechanically if at all.

I think we are agreeing.

The mix between the two viscosities is was I am against. You cant set 15w40 VR1 by mixing 10w30 and 20w50 ,, it does not work that way

agree on TMOG opinions.

 

[FusilliJerry]

I think we are agreeing.

The mix between the two viscosities is was I am against. You cant set 15w40 VR1 by mixing 10w30 and 20w50 ,, it does not work that way

agree on TMOG opinions.

I meant ditching SP add pack for more detergents.

To your point on the mix I had read elsewhere with such an “experiment” in mixing VR1 viscosity and a 50/50 mix came out too thin for a real 15w40. To that end that’s why I went 2qt 10w30 to 4qt 20w50. I doubt still that it’s perfect but I’m personally just shooting for order of magnitude. Mine seems to purr like a kitten on it vs. 6qt 10w30 on a 90+ degree day so I’m happy enough. Back to all 10w30 come fall.

The only other oil I’d consider experimenting with is PYB considering it’s history of low wear in 4.0s but all the UOAs I’ve seen on it are nearing 10 or so years old and zinc appears quite low in later VOAs. Maybe I’ll spring for the UOA one of these changes as the guinea pig.