Mobil 1 FS 10W-30 Jeep 4.0L 3000mi OCI

[MechEng13]

I am a new member, but I have been using the information on BITOG for a few years. Recently, I bought a '95 Jeep XJ with about 95,000 miles. Since owning it, I replaced the timing chain, rear main seal, & water pump. Considering the new internal parts/seals, the Fe & Si ppm are not going to be accurate or useful. This UOA was more of a way to verify the additive package in the Mobil 1 & give me peace of mind that I have a good motor.

Here are the specifics:

Oil: Mobil 1 Full Synthetic 10W-30 (not the HM, EP, or other. Just standard FS).
Oil Filter: Mopar 090
Air Filter: AEM Dryflow
Fuel: Ethanol-free 89
Other: Magnet used on the outside of the oil filter
OCI: aprx. 3,000 Miles

I have heard/read many "bad" things about running Mobil 1 FS in a Jeep 4.0L, but I have always had great results in my other daily drivers and decided to use it anyways. After dropping the Mobil 1, I switched to Valvoline VR1 10W-30 Full Synthetic. I plan to run that oil for 3-4K miles and send in a sample to ALS labs next year. Contrary to internet myth, the greater ZDDP level in VR1 FS is not necessary for the 4.0L and most likely will not improve wear characteristics. BUT the oil is a neat blue shade & there's a cool American flag on the bottle, so I figured my Jeep needed it.

All joking aside, I like the additive package of the new Valvoline VR1 FS and the HTHS values (7.8cP & 3.25 cP @ 100C & 150C respectively). It is the only oil I could find that has slightly more zinc but still retains a decent amount of detergents. I will report back with the new UOA results next year.

 

[SubieRubyRoo]

Silicon is the only really concerning thing, and may be leading to higher iron numbers. 9ppm/1k miles seems high but I don’t peruse many Jeep UOAs. Check your air filter seal & fit, along with the intake piping. Make sure everything is sealed and snug. Monitor & report.

WELCOME!

 

[Greasymechtech]

Consider a 0w40 or 5w40

 

[Zaedock]

Consider a 0w40 or 5w40

I recently changed my trail YJ (2.5L/SM420 transmission/Atlas T-case) to Castrol 0W40. Runs nice.

 

[LouC]

Make sure that the air filter is properly installed & the clips on the housing are all properly clipped in place. I had this same issue on my 07 Jeep 5.7, one of the clips was missing; when I changed it to a Mopar cold air intake the silicon actually went down.
BTW I also have one of those Jeep 4.0 just did my first UOA @ 181,000 miles and it came out surprisingly well. I’ve been using Valvoline Max Life 10/30 or 5/30.

 

[KCJeep]

That's lower than average iron numbers for Mobil 1 in a Jeep 4.0, but still a bit higher than what you would probably get with Rotella, Maxlife etc. Viscosity is a bit lower than I'm comfortable with for a Jeep 4.0 as well.

As mentioned above already, a 5w40 is about perfect for a 4.0 and can be found in "Euro" options with a high level of additives friendly to the venerable 4.0.

 

[Zaedock]

I recommend searching through old threads from a member named Gary Allan, who passed away in April of 2011. He ran some custom ultra-low viscosity brews in his Jeep TJ. Interesting reading from a super cool guy (RIP).

 

[SC Maintenance]

Consider a 0w40 or 5w40

Aren't most of those oils low SAPS - which might be counterproductive with an engine of that vintage?

 

[Greasymechtech]

No, most aren't low SAPs

 

[MechEng13]

Thanks guys! I appreciate the replies.
I am not concerned about the silicon level, considering the oil pan gasket, thermostat housing gasket, timing cover gasket, and water pump gasket were all replaced while this oil was in use. I always use a light coat of Permatex on the mating surface for a perfect seal.

From what I have read, the Iron number is average for a Jeep 4.0L. These Jeeps seem to shed more Iron than most! Over all, I am happy with Mobil 1, and would not be afraid to use it in a 4.0L again. That said, like you all have mentioned, there are better suited oils for a tractor engine like the I6 4.0L. For whatever reason, cheap Pennzoil yellow bottle seems to be the flavor of choice for Jeep owners. I might run that oil once it is time to drop the VR1. I have also heard great things about Amsoil Signature Series, but can't bring myself to pay the price.

 

[addyguy]

Pennzoil YB 10W-30 is a great fit these engines it seems.