all i run in all of my vehicles(all gas motors, even run motorcraft in my chevy). i run mobile 1 in my girlfriends volvo, but that twin turbo inline six is a little higher performance than the rest, and requires a synthetic blend at minimum according to volvo, and i dont argue with factory testing...they spend a lot of money to determine oils and viscocity levels. i do like the idea of synthetic oils, they tend to hold viscosity longer according to the majority of testing, but if you do your oil changes regularly, i dont think the extra cost is nessisarily worth it since i have seen 7.3's with 500k or more running nothing but regular old motorcraft oil. i think as long as it is a good oil, it really doesnt matter what you run as long as you maintain your vehicle at decent intervals. its not so much the supberb quality of the oil (as long as it is a good oil) put in during the oil change, as much as it is the quality of the oil in the motor at every given point in its life.