Oil for Jeep 4.0 Engine

[fins]

For the past 20,000 miles I have been using Rotella 15-40 in my 2005 Jeep Wrangler.
I use a 5,000 OCI.

I am thinking about switching to a 5w30 oil for better flow on cold start.

With all the talk about flat tappet engines, ZDDP, oil shear, etc... I am getting confused about what oil to use.
What's more important shear strength or ZDDP levels?

I was considering Mobil 1 or QS Defy..........just wondered what others would be recommended?

 

[dparm]

15w40? Yikes -- been doing a lot of severe duty stuff? Is that motor even spec'd for that? Rotella is a good oil but was probably way too thick for you.

I would absolutely run a 5w30 in that motor. If you are doing a lot of "severe duty" things in the car, like towing or off-roading, go for a full synthetic. Otherwise I would say that any semi-syn or conventional that's on sale would work well.

 

[RamFan]

For 5k mile OCIs, I'd give 10w30 T5 a shot.

 

[racer12306]

Our 02 WJ 4.0 ran great on 5w40 Rotella. I'd agree 15w40 is way to thick at cold start.

I'd also imagine RamFan is on a good track with the T5 10w30.

 

[cp3]

Well there is always a lot of talk about these engines liking a heavier oil. I think the Defy might be a good option but see what some people who know more about the 4.0 say.

You could always go with something lighter in the winter when the differences in cold start properties are more pronounced.

Another option may be to go with a 5 or 0w40.

 

[Hollow]

Typically a 10w30 may be a bit more shear stable than a 5w30, but the 4.0 engine is a solid performer. I would think you could run a 5w30 year round, unless your manual still calls for a 10w30.

Unless you are using is HARD, I'd go with:
PYB
QS Defy
Rotella T5 10w30
Rotella T6 5w40

 

[SwampSurvivor]

Rotella semisyn 10w30 or T6 5w-40

 

[Bandito440]

Rotella T6.

 

[MrRPM]

I like to mix quakerstate DEFY 5w-30 with DEFY 10w-40 for my jeep.

 

[ChemicallyChargd]

Well to clear some confusion, I won't argue zinc benefits flat tappet rides, but there's some confusion as to why or how. Zinc is not in any way nor does it form any kind of magical coating on parts, a high zinc level will only allow the motor oil to last longer before it's supply of zddp is depleted. Using a motor oil that has such a zinc level that it can't be API certified or adding it in has been proven to do more damage to your cat's, far more damage than its worth, like trading your dollar for a penny. So essentially don't worry about the zddp, if it's API certified it's got plenty zddp to last through a 5k-7,5k mile OCI, it would only concern me if I were considering 10k+mile OCI' s(what I do currently). Shear strength is the single most important thing you want, if this sucks, it defeats the point of a good additive pack. Take it all the way and use their 0w-30, the viscosity at room temp is closer to the operating temp viscosity, which means less viscosity modifiers and a higher total base stock % (less additive means more actual oil), both being the same op. temp viscosity, the 0 will get moving quicker at lower temps than the 5. Remember the problem with oil is it thickens when it cools, NOT that it thins when it gets hot, the 0w thickens less, if nearly all wear is in those few seconds at cold start(after its warmed up the oil can get moving almost instantly and can be started/stopped with no where near the wear of a cold start), and the 0w gets to your bearings faster, it's the intelligent choice.
-SRV

 

[SwampSurvivor]

Higher ZDDP levels wouldn't be a problem unless you were burning large amounts of oil. 4.0s leak oil ... they rarely burn it.

 

[buster]

Mobil 1 High Mileage 5w30 would be a good fit. SL levels of ZDDP. Rotella 5w40 is another good option.

 

[Nick R]

I'd use a good 5W-30- I have my sister/friend running QS Defy 5W-30 in her 98 JGC with the 4.0L with a Mopar filter.

 

[Kira]

Hello Sis' '99 XJ w/171K purred when we sold it. 5W-30 dino "all the time-by the book", 10W-30 dino for a Summer time oil change. The engine was clean clean as a whistle. It would use a pint over 5,000 miles. Kira

 

[gregk24]

I think the 4.0 likes Pennzoil Yellow Bottle. 15w is too thick for that engine on start up. Maybe try a 10w30 or 5w30. What does it spec? Just use whatever it specs and you will be fine.

 

[dparm]

Originally Posted By: gregk24
I think the 4.0 likes Pennzoil Yellow Bottle. 15w is too thick for that engine on start up. Maybe try a 10w30 or 5w30. What does it spec? Just use whatever it specs and you will be fine.


Spec is 10w30.

 

[Chris142]

Yup spec is 10w30 above 0f. Imo nothing wrong with the 15w40 in it. They show better wear numbers with thicker oil.

How much difference is there between 10w30 and 15w40 @ 100f anyway?

 

[TXCarGeek]

Originally Posted By: ChemicallyChargd
Well to clear some confusion, I won't argue zinc benefits flat tappet rides, but there's some confusion as to why or how. Zinc is not in any way nor does it form any kind of magical coating on parts, a high zinc level will only allow the motor oil to last longer before it's supply of zddp is depleted. Using a motor oil that has such a zinc level that it can't be API certified or adding it in has been proven to do more damage to your cat's, far more damage than its worth, like trading your dollar for a penny. So essentially don't worry about the zddp, if it's API certified it's got plenty zddp to last through a 5k-7,5k mile OCI, it would only concern me if I were considering 10k+mile OCI' s(what I do currently). Shear strength is the single most important thing you want, if this sucks, it defeats the point of a good additive pack. Take it all the way and use their 0w-30, the viscosity at room temp is closer to the operating temp viscosity, which means less viscosity modifiers and a higher total base stock % (less additive means more actual oil), both being the same op. temp viscosity, the 0 will get moving quicker at lower temps than the 5. Remember the problem with oil is it thickens when it cools, NOT that it thins when it gets hot, the 0w thickens less, if nearly all wear is in those few seconds at cold start(after its warmed up the oil can get moving almost instantly and can be started/stopped with no where near the wear of a cold start), and the 0w gets to your bearings faster, it's the intelligent choice.
-SRV


I ran M1 AFE 0W-30 in my TJ from July-March this past year and it did fine on it. After looking on here though, I saw that for the temps that I see here Texas, at start-up, the 5W and 0W viscosity were [censored] near the same. It wasn't until extreme sub-zero temperatures that the cold cranking advantages of the 0W came in to play. Because of this and the lower zddp levels in M1 AFE, I switched back to M1 5W-30. Has the same viscosity in the temp ranges that my Jeep will see and a bit more zddp.

 

[901Memphis]

The rotella T6 5w40 has probably racked up so many miles in those engines I'd probably use that if I had one. If you're concerned with iron wear use a5w40. If you want better gas mileage try a 0w30 like mobil 1 AFE or do some extended drains with Amsoil signature series 0w30.

 

[Errtt]

PYB 10w/30 or Rotella T6 5w/40