I have just found out for sure that my 4.0 Jeep engine has indeed had synthetic oil in it for the last 195,000 miles. I'm giong to be changing all the fluids, but I don't think I'm going to be paying 30 bucks for mobile 1 right now, but maybe in the summer when I'm towing my boat. What about synthetic blend? What are the benefits of that over dino oil? Is it worth the extra price?