Because diesel is more expensive than gas and as little towing as you do, I would go the gas route. You might get worse mileage during your occassional towing trips, but $.50/gal less for every day driving will be more economical in the end. Of course we are talking a 3500 series truck, right? Neither one will get much mpg so it comes down to do you like the smell of diesel, do you have plans for building a biodiesel 'cooker' or do you like knowing you can get gas any where?