I have noticed that my F350 seems to get better mpg in the rain. I made the same delivery to Conn for years and when it was raining I seemed to get more miles per tank. When I checked my fuel mileage I would average 13-15 mpg. Well yesterday I made a run to NH in the pouring rain before the return trip I topped off. 11.5 gals I went 191 miles so I got just over 16 mpg. I never ever got over 15 mpg ever. My truck is a 94 factory turbo CC dually 5 speed 4.10's. I purchased the the truck with 200K it now has almost 300K and has some blowby. With 300K and blowby I should be gettin less mileage, I did put in new G code injectors maybe 40K ago but still run the same pump and haven't changed rear tires in years. Does the diesel engine turn the mosture into super heated steam or something? Anyone else ever notice this