You may get high teens around town empty. Not likely to happen with an enclosed trailer in tow. The cummins is easy on fuel but light towing and empty truck you aren't likely to see mush improvement over your 1/2 ton chevy. I'm guessing you can squeak out 20mpg highway and maybe 10-13mpg towing? The dodge will probably match this and do the work with ease but you won't be saving on fuel really.