WilliamTK1974

Hello everyone,

I have a 1996 Cherokee Country with 303k miles on what appears to be the original drivetrain. For the most part, I've felt pretty confident that I can take it almost anywhere. I've owned it since January of 2021 and have done quite a bit of work on it to make it a better driver and have kept up with its maintenance. I didn't get much information about its history from its previous owner.

Shell Rotella oil seems to be popular in the XJ community for higher mileage engines because even though it may have the same viscosity as an oil made for gasoline engines, it's "thicker" and may help to keep the engine quieter and the oil pressure higher. My engine has a bit of a growly, piston-slappy sound when cold started, but it gets quieter as it warms up. That said, it's never completely quiet. I'm not afraid to drive it, but it may be showing its age. Also, after a freeway ride on a hot day, when I hit the first stop sign or traffic light, the oil pressure gauge goes really low until I start rolling again. I know from a technical standpoint it's within acceptable limits, but it sure looks odd. The most oil I've ever seen it use was getting to the halfway range of the Safe marking on the dipstick, and it's only done that one time in my ownership, so it's not using much oil. It may go down about 1/4 of the Safe range in between oil changes.

So, last oil change a little over a week ago, I decided to use Rotella T6 10W30 in it, along with the Mopar oil filter whose number ends in 090. Six quarts and I'm right at the top of the Safe range on the dipstick. The engine may be a little quieter, and the oil pressure gauge does read higher even after a hot highway run.

We had some really hot days over the last couple of weeks, and it has cooled down and feels more temperate since the middle of the week. But over the last couple of days, I swear I'm hearing pre-ignition in certain driving situations. While it could be bad gas, this doesn't seem probable. I use Top Tier maybe 70% of fill-ups. I know that's more a function of detergent rather than octane or quality, but it has to count for something. But the reason it's a concern is because it hasn't happened before. The oil is the only thing I've done different recently. I hate to be wasteful, but I'm tempted to drain it and just go back to using SuperTech High-Mileage synth or regular 10W30. Nothing wrong with that oil. It's made by Warren and has to pass the same tests that the brand-names do.

Any thoughts? I hate hearing that pinging sound and know how bad it can be for the engine, so anything to get rid of it would be great. But the only thing that seems different is the oil.

Thank you,
-William

SimpleDad

When I first got my XJ running I put Rotella in it because of the internet hype. It felt/sounded wrong to me and I switched it out and have been happy (I grew up riding in this XJ. It's seat of the pants feel/sounds are ingrained into me since my mom took delivery of it).

Is this going to give you stress or reduce your enjoyment of driving your XJ? And if it is is ending that worth $50 and a half hour to you? It was to me. There's enough other sounds/vibrations that my mind is trying to evaluate I don't need another worry. Unlike mechanical/electrical advice that I can validate myself the whole Rotella in an XJ thing seem pretty subjective and 'this should make sense'. It definitely makes the engine run and sound different. Is that bad? I don't know, and I don't care to find out.

RockyMtn96XJ

I've run all 3 types of rotella in my jeep. T4, T5, & T6 depending on what may be on sale. I had no issues during those times and have even gone back to "regular" oil in between, and after, using those. The rotella and other oils normally used in diesel applications has extra zinc and other additives that help flat tappet motors like the 4.0, providing the extra "lubrication" for the cam and lifters. If I run "regular" oil, I will add a bottle of additive that contains the ZDDP stuff. Thats essentially the same thing that is already in the rotella.
All I can think is using the rotella has possibly changed the sounds due to the extra lubrication and now things run smoother allowing you to hear more noises, or somehow.... well I dont know what else it could be. MAYBE, just MAYBE deposits somewhere were dislodged and those tiny bits are causing the noise. But I highly doubt that. Just a feeling though.
You could always take a sample and send it to Blackstone or another oil analysis place to have it analyzed for contaminants. Maybe even put a strong magnet on your oil pan to see if its catching anything. Amazon sells cheap neodymium magnets If a magnet doesnt stick, because I dont know if the pan is magnetic, you could use a magnet to gather anything that may be in the bottom of the pan and drag it over to the drain hole so it can be in the flow of oil as it comes out the drain hole by sliding it around the outside of the pan... if that makes sense. Or stick the magnet to the oil filter. Or use a magnetic drain plug. Certain contaminants will tell you if you have a lot of wearing on internal parts, like copper, aluminum, and obviously iron.

awg

My XJ pings on lower octane fuel (even though it is specified)

That is (Australian) 91 octane (Oz is different to US) I think that is US 87

So I use E10, which is 94 Octane and the pinging is dramatically reduced (it is also the cheapest fuel)

95 or especially 98 fuel is premium priced

I dont know what US octane rating you are using?, it can be converted online

I doubt it would be the oil. I use 10W-40 in a hot climate

robsjeep

Is the knock sensor working? is the engine getting too hot? how about spark plugs, how they look? intake leak? mixture ok?

oil brand should not effect knocking

awg

I dont think there is a knock sensor on the '96 models

Please correct me if i am wrong

changing my spark plugs improved the pinging a lot, and they were 4 yrs old, but only 25k miles, Campions as per spec.

I didnt expect them to be crook, and I was surprised when it didnt fully cure the issue.

running 94 octane made the pinging almost go away, I haven't tried 95 0r 98, maybe i will in summer when the problem is worst

There is an adjustable MAP sensor mod

check live data on OBD2

Tsaani97xj

Just my opinion from my experience with my 320k 4.0.

Carbon build up is the most likely cause of your pre-detonation, pinging. Higher octane can reduce the ping all while increasing carbon build up. Your ignition system is designed or tuned for lower octane. When you use higher octane you do not burn all of the fuel effectively which adds more carbon.

A bottle of water and steam clean your valves and I would bet your pinging gets drastically better.

My engine knocked so bad you would swear it would throw a rod any second. It drove for 25k like that. I sold it still running sounding like that and moved on.

Best of luck.