I purchased my KJ 2002 3.7L 4x4 w/Auto last year in July I immedeiatly changed everything over to Amsoil with almost 90,000 miles on this Jeep I had no qualms about swithing over to Amsoil from Bunper to Bumper. If you do not see any oil burning issues then your good to go . Do understand that if you have any leaks or Oil burning issues due to Amsoils high detergent quality if a leak or oil burning issues Amsoil will increase the use of oil due to Amsoil's high detergent quality. But if these are any of these issue by all means upgrade to synthetic. In fact if you want to trake things a step further look into Amsoils oil by pass filteration system. With the addition of this filteration issues you will filter your oil to the point that you do not have to change other then every couple of years. Years ago after purchasing a Toyota Celica, I had some scratches on both the driver and passenger windows, I had already converted everthing over to synthetic. Upon bringing it back to the dealership for warranty repair. My Brother in law who relished any chance to dig into me, informed me that I will never bad mouth your funny oil again.

I then proceded to ask what had , changed his attitude upon which he responded that after all his years working for car dealerships my Toyota with Amsoil not only ran better it was quiterer and more respnsive then any other car on the lot. Considering that my Brotherinlaw enjoyed every opertunity to abuise me, no other praise could ever be offered. So If there are any doubting Tomiches out there Amsoil is the best today or tomorrow or down thew road