Okay, so I'm going to add to the discussion/confusion over engine oil. I just bought a 2003 TJ Sport and my 4.0 is ticking intermittently on startup and sometimes after that at idle. I've scrambled my circuits reading about lifters, ZDDP, ODPA's, Oil Filters and Oil. I only want to post this because I couldn't find anything through a search on this subject yet I found it very interesting. I was sifting through service bulletins for late model TJ 4.0 models and found 09-013-04 issued for the 2005 model year (and only that model year). When you read this paragraph from it you'll see that it applies to all model years...
"Only use API Certified engine oils that meet the requirements of Chrysler's Material Standard MS-6395. MS-6395 contains requirements, not addressed by API Certification, that provide additional protection for Chrysler Group engines. All Chrysler Group gasoline engines, irrespective of model year, should be serviced with API Certified engine oils meeting MS-6395. Chrysler Group Engines are developed, certified and filled with engine oil of the designated viscosity grade, meeting MS-6395, and should be serviced with the correct viscosity grade engine oil. The following table contains the correct viscosity grades for the 2005 model year."
That got me searching through oils. My current oil is Mobil 1 High Mileage which didn't do anything for my tick btw, at least not yet. Now I know they're probably not related but I noticed that Mobil 1 does not have the MS-6395 certification. I certainly understand that this could just mean that Mobil didn't get that particular oil certified, but, I did notice that Mobil Super is certified to MS-6395. Check out the Mobil website...
From what I read on their website, Mobil Super is simply their conventional oil (yet they offer a synthetic version, which is confusing) and Mobil 1 is their "Advanced Synthetic".
Does anyone have experience with Mobil Super? Searching for Mobile and Super doesn't get me very far. Anyone have thoughts/knowledge pertaining to MS-6395?