I use Rotella T dino in my car and in my diesel boat motors and none of the engines use oil. The Rotella T dino is widely used in commercial truck fleets. R-T dino keeps engines clean. The R-T syn doesn't have as low a pour point as M-1, but in Va. you should be just fine.In Alaska, I'd go for the M-1. The main thing is to change the oil often. I change at 3000 miles, thus I don't think that syn-althought superior to dino- is worth it unless I move to a cold climate.