1998 4.0L Jeep Cherokee Oil Suggestions

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WranglerTom

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Mar 6, 2007
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Location
Ohio
Good evening everyone,

I'm new to this website and can use some suggestions on what type of oil I should start using in my Cherokee. I just received a UOA from Blackstone Labs--the first UOA I have ever received.

I purchased this vehicle used in the year 2000. It had 21,000 miles on it when I bought it. I have used Mobil 1 10w30 fully synthetic in it since day one (of me owning it).

First, when looking at the averages compared to my score, which numbers should be high and which numbers should be low? Second, my research shows that Jeep 4.0L engines have high iron wear with Mobil 1 synthetic oil (wish I would have known this 6+ years ago!). I don't know what to do about the aluminum wear.

What brand and type of oil will provide the best engine wear and alleviate my higher-than-average iron and aluminum wear?

Check out the UOA results:

EQUIPMENT MAKE: Jeep
EQUIPMENT MODEL: 4.0L Inline 6 cyl
FUEL TYPE: Gasoline (Unleaded)
OIL USE INTERVAL: 3,452 Miles
OIL TYPE & GRADE: Mobil 1 10W/30
MAKE-UP OIL ADDED: 0 qts

TOM: Universal averages show typical wear metals from this type of engine after about 4500 miles run on the oil. Your oil was in use 3452 miles, yet we found iron and aluminum reading higher than average. Neither is high enough to call a serious problem, though we would like to see another sample next oil change to keep an eye on them. They are coming from the upper end. No moisture or anti-freeze was present that would be causing the wear. Everything else looks good. The TBN read 4.1, still active additive remaining. Stay at 3000-3500 miles to monitor.

TOM'S JEEP / AVERAGE
ALUMINUM 7/3
CHROMIUM 1/1
IRON 74/25
COPPER 3/4
LEAD 5/4
TIN 0/1
MOLYBDENUM 96/54
NICKEL 2/1
MANGANESE 0/1
SILVER 0/0
TITANIUM 0/0
POTASSIUM 8/2
BORON 50/44
SILICON 7/11
SODIUM 11/10
CALCIUM 2636/2044
MAGNESIUM 17/155
PHOSPHORUS 639/716
ZINC 726/861
BARIUM 0/0
 
I have a '99 4.0 Jeep and I would suggest Amsoil ATM 10W40 or Shell Rotella T 5W40 for it. Both oils work well in a 4.0
 
Your air filtration isn't terrible, but it could be better. I doubt though that it is the sole cause of such high Fe and Al numbers. I would look for air leaks and replace the filter.

Since you are looking to optimize the UOA's on this engine I would start with Auto-RX application(s).

What is your driving routine? How many miles on your XJ? How many miles per year?

I think that your 4.0 may indeed be a good candidate for thicker oil. KW lists some good choices. I have also had good results with Amsoil 5w-40, Mobil 1 5w-40, and GC. Others will likely chime in to suggest other oils that work well.
 
Quote:

Your air filtration isn't terrible, but it could be better. I doubt though that it is the sole cause of such high Fe and Al numbers. I would look for air leaks and replace the filter.

Since you are looking to optimize the UOA's on this engine I would start with Auto-RX application(s).

What is your driving routine? How many miles on your XJ? How many miles per year?

I think that your 4.0 may indeed be a good candidate for thicker oil. KW lists some good choices. I have also had good results with Amsoil 5w-40, Mobil 1 5w-40, and GC. Others will likely chime in to suggest other oils that work well.

Click to expand...
Ditto..
 
Quote:

Your air filtration isn't terrible, but it could be better. I doubt though that it is the sole cause of such high Fe and Al numbers. I would look for air leaks and replace the filter.

Since you are looking to optimize the UOA's on this engine I would start with Auto-RX application(s).

What is your driving routine? How many miles on your XJ? How many miles per year?

I think that your 4.0 may indeed be a good candidate for thicker oil. KW lists some good choices. I have also had good results with Amsoil 5w-40, Mobil 1 5w-40, and GC. Others will likely chime in to suggest other oils that work well.

Click to expand...


My wife routinely drives this vehicle. The drive consists of a brief two minute warmup, followed by a 20 minute drive in stop and go traffic for approxiamtely eight miles. Speeds average between 25-40 mph. The truck has a little over 85,000 miles on it. She averages about 9,000 miles a year. She's a teacher, so the truck sits a lot during the sumer when school's out. Since we live in Northeast Ohio, I would prefer not to use a thicker oil. I also prefer synthetic because of the benefits in varying temperature conditions and for vehicles that sit a lot.

As for the air filter and air leaks, I'm going to be working on solving that problem today.
 
What were the fuel numbers from Blackstone? You may be seeing the effects of a fuel dilution issue as well.

Depending on when that sample was taken the Fe may be from corrosion from sitting.
 
Does this jeep sit for several days or a week at a time? Could be corrosion is generating the elevated results for iron. If this is a recent OCI that includes the winter months, this would also explain the slightly elevated numbers for Alum & Lead.

Also, the sodium number would seem to indicate that this engine has seen some winter driving & ingested road salt, as it’s not an additive in this motor oil.

The single digit silicon level indicates no problem with air filter leaks.

The results from this UOA are not anything to be alarmed about. Switch to another oil, away from M1, and run another UOA to see if the iron levels can be knocked down.
 
Quote:

What were the fuel numbers from Blackstone? You may be seeing the effects of a fuel dilution issue as well.

Depending on when that sample was taken the Fe may be from corrosion from sitting.

Click to expand...


Fuel number was only .5. The sample was taken immediately after a 30 mile highway drive (my commute home from work).
 
Quote:

Does this jeep sit for several days or a week at a time? Could be corrosion is generating the elevated results for iron. If this is a recent OCI that includes the winter months, this would also explain the slightly elevated numbers for Alum & Lead.

Click to expand...


The oil was in the engine from 10/4/06 to 3/11/07. The Jeep is used five days a week, with maybe a trip to the grocery store every second or third Sunday (it usually gets weekends off
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). It sat for a couple days at Thanksgiving and for 3-4 days at Christmas/New Years. It's been sitting outside for winter because I needed the garage as a workspace for some home improvements.

Ay recommendations on what brand synthetic oil and viscosity to try? What about an oil filter? I've been using OEM Jeep filters.
 
Keep in mind that your Jeep UOA wear metal numbers are just slightly elevated & nothing to get alarmed about.

This is a short trip vehicle and I would shy away from the the 40 weights as the oil is just getting up to full operating temperature at the end of the 8-10 mile daily work drive. With a 40 weight, the oil will spend a good portion of the drive in the +20 cSt range and this will not help with fuel economy.

Just switching away from M1 is going to knock down the Fe number, as M1 always shows higher UOA iron numbers.

For a readily available OTC brand, Pennzoil Platinum 10W-30 is a good option. It has a great Noack volatility rating and Teryy Dyson is speaking highly of the results showing up in UOA wear numbers.
 
Can you provide a link of a UOA for a Jeep 4.0 with Pennzoil Platinum? I've been looking but I'm new and can't find anything. Who's terry Dyson?
 
Motorcraft 5w-30 is one of the thickest 5-30's and it can easily make 3500 miles OCI.

Synthetic is a good choice for your winter climate and Pennzoil Platinum 5w-30 European Formula is also thick.
 
I have used Amsoil 0w-30, mobil-1 10w-30, and rts 5w-40 currently. The Jeep likes the 0w-30 as far as gas mileage. I think the 5w-40 is a little thick and gas mileage is down.

I am looking at the german castrol 0w-30 for the next oci.
 
My '99 Cherokee has 275,000 miles on its 4.0 with no engine problems ever. I used Mobil 1 from the 5,000 mile point up until 200,000 miles at 5,000 mile OCI, then switched to Amsoil at 15,000 OCI. The engine still doesn't burn any oil. I think you would be a great candidate for Amsoil 5W30 with the new 15,000 mile rated Amsoil oil filters at one year OCI.
 
Warchild, what is the reduction number for your gas mileage with the Shell Rotella Syn? I bought two jugs of that recently intended for summer use in my 4.0. Currently using GC 0w30 and the Cherokee loves it, hover around 20(+)mpg typically with that oil. How does your 4.0 run/idle with the rotella?
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Quote:

I have used Amsoil 0w-30, mobil-1 10w-30, and rts 5w-40 currently. The Jeep likes the 0w-30 as far as gas mileage. I think the 5w-40 is a little thick and gas mileage is down.

I am looking at the german castrol 0w-30 for the next oci.

Click to expand...
 
Quote:

My wife routinely drives this vehicle. The drive consists of a brief two minute warmup, followed by a 20 minute drive in stop and go traffic for approxiamtely eight miles. Speeds average between 25-40 mph. The truck has a little over 85,000 miles on it. She averages about 9,000 miles a year. She's a teacher, so the truck sits a lot during the sumer when school's out. Since we live in Northeast Ohio, I would prefer not to use a thicker oil. I also prefer synthetic because of the benefits in varying temperature conditions and for vehicles that sit a lot.

As for the air filter and air leaks, I'm going to be working on solving that problem today.

Click to expand...


Hello and
welcome.gif
from Southwest Ohio!

The Jeep's are notorious iron producers, but nothing to worry about yet on your UOA IMO. I have a 92 XJ that loves Maxlife Semi-Syn. Good oil, good price, and she just runs smooth as can be at 163k. GTX, Havoline and PP all seemed to idle a little rougher (I'm sure they were protecting the engine fine), but the Maxlife has kept it running smoother than anything I ever put in there. I haven't tried Maxlife Full Synth in it, so that may be an option if you are looking for an extended OCI......
 
The Al, Fe, and Pb numbers are definitely elevated from ideal.

Oil really isn't the issue at this point with this engine, rather it's air filtration and fuel dillution. I do think that you would benefit from a thicker oil, better air filtration, and perhaps a tune up.
 
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