May regret using Rotella in my '96 XJ

[WilliamT1974]

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 got very little 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

 

[Tim_MN]

Add a bottle of Techron fuel injector cleaner and fill the tank with gas from a different gas station.

Oil pressure is a direct result of the engine rpm, lots of Jeeps have driven lots of miles with less than perfect oil pressure. When using a 1960's designed engine, regularly changed oil is about the only oil requirement that is necessary. 10w-40 oil may be a better choice, or not. I use 20w-50 in my 1984 CJ-7.

 

[Unclewolverine]

10w30 synthetic is too thin, especially for a high mileage motor. I ran regular 15w 40 rotella in my mail jeep from 180k to when it was totaled at 416k. Still held 25 psi oil pressure at hot idle on 100 degree days. Also just used cheap crappy gas, it never cared.

 

[Anak]

I agree with Tim's diagnosis, but I would be inclined to go even farther and send your injectors out to someone who can measure their flow rates and make sure they are all balanced.

I was having detonation problems with my '96 and went through an entire series of fuel treatments and sensor trial and error tests. None of those things made a difference. The fuel system treatments would have been the right idea, but they made no difference (IIRC I ordered a Berryman product which was supposed to be the bee's knees). I swapped in a serviced set of injectors and the problem was solved. I then sent out my original injectors and the testing showed they were all over the map for flow rates, and one of them was super lean. The computer could not compensate for that injector.

 

[Bent]

Berryman product which was supposed to be the bee's knees

Redline, then Heat or equivalent. Knock sensor/connection?

 

[Anak]

Knock sensor?

Knock sensor?

I don't have no stinking knock sensor!

Them's are on your Renix motors. Chrysler's bean counters got rid of them. Along with those chrome strips in the cargo area.

 

[Bent]

Knock sensor?

Knock sensor?

I don't have no stinking knock sensor!

Them's are on your Renix motors. Chrysler's bean counters got rid of them. Along with those chrome strips in the cargo area.

In the infamous words of Nana Rosanna Rosanna Dana, never mind.

 

[75SV1]

A lot of questions. I have run Rotella 10w-30 in my XJs at time. I had no issues. They recently introduces 10w30 T6 or full synthetic. I have not tried it. I use to run the 10W-30 T4 in my MB240D for the winter time. Then the 15W-45 the rest of the year. Also, the same on the XJs and MJ.
What are to OCIs (oil change interval)? Also, 1/4 to 1/2 quart in say 3,000 miles is actually good. I would question where it is losing or using the oil. If from the valves, then the oil is getting into your fuel mixture. Thus lowering your fuel octane. Also, could be 'true' blowby, from the rings. Again, lowering your octane.
Also, what is your oil pressure? It should be above 13 psi at idle, when up to temp. My mini stroke is new. It is around 55 psi at 2,000 RPM and say 40 psi at idle warm. The engine I replaced ay 280K, had similar numbers, surprisingly. Other XJ motors were around the 15 psi at idle and say 35-40 psi at 2,000 rpm.
So, possibly yours needs new valve stem seals.