The owner's manual does specifiy 5W20, as the recommeded API rating for weight and viscosity. However, it is NOT synthetic. The original oil in the car from the factory is Mopar. However, when you take it to the dealer for an oil change, they will use Mobile1, NON-synthetic. It is a 50/50 mix, so it blends well with the original oil. Hope this helps. However, did you check it when you bought it? Have you noticed any drips or other signs of leaks? If you have, take it in as soon as you can. If nothing else, something just may be loose. Worst case, you could find something that noone else knows about, and maybe Jeep could do something about it. I checked all my fluids on the dealer's lot, so I knew where I was sitting before I drove it home. Like I said, hope this gives you an idea!