I have a 2000 Jeep XJ (Cherokee) with the 4.0. It has been in my family since the beginning, first with my dad and then with me when I got my license. It has 75,000 miles and runs perfectly. I decided that I wanted to run synthetic oil in it, so for the past two changes I’ve used 10w-30 (the recommended weight) Mobil1 Extended Performance. Ever since the switch I’ve noticed a piston slap (“chattering” noise) at start-up that eventually goes away. This isn’t an all that uncommon occurrence in the 4.0, but if it wasn’t there before the M1 I want to see if there’s something I can switch to that gets rid of it. I don’t know what type of oil was in it before I used M1 because it was done at a shop.
Some other info: I primarily use the Jeep as a daily driver, but I do off-road it on occasion. I live in NJ where the temp never goes below 0*. My typical trip is less than 5 miles, and I drive it easily. I change the oil yearly or after about 7-8K miles, whichever comes sooner.
On a separate note, I’ve noticed that a considerable amount of Jeep owners run oils like Rotella T6 or Mobil Delvac in their engines because they have more ZDDP (4.0’s are flat tappet). I would be open to this, but I’d really like to stay synthetic and Mobil Delvac 1 and Rotella T6 are 5W-40 (rather than 10w-30, which I’ve been running).
Any suggestions/advice would be great.
Some other info: I primarily use the Jeep as a daily driver, but I do off-road it on occasion. I live in NJ where the temp never goes below 0*. My typical trip is less than 5 miles, and I drive it easily. I change the oil yearly or after about 7-8K miles, whichever comes sooner.
On a separate note, I’ve noticed that a considerable amount of Jeep owners run oils like Rotella T6 or Mobil Delvac in their engines because they have more ZDDP (4.0’s are flat tappet). I would be open to this, but I’d really like to stay synthetic and Mobil Delvac 1 and Rotella T6 are 5W-40 (rather than 10w-30, which I’ve been running).
Any suggestions/advice would be great.