I recently read a cost analysis on one of the boards I frequent but now I am unable to find it again. Perhaps it was here. It was about a guy from Texas who owned a business that had 8 Ford 4x4s which he had equiped 4 with full synthetics from mobil in the engine and tranny and the other 4 with dino. The vehicles had about 425k miles each when he sold the company. The results were the best advertising I could have ever seen for the use of synthetics. It really illustrated the price-vs-cost differences.