Something you also have to consider is what you will pay in maitenance costs for a diesel as well. I do not know this from experience, but my boss just bought fuel filters for his Cummins and they cost about $30 a filter. And that's not to mention the additives he runs in his fuel once or twice a week, and you have the cost for oil which he buys amsoil for his truck. From all the information I seem to be getting it seems like a gas rig would be a less expensive way to go unless you have the money to do all the maintenance on a diesel. But I will agree with buying a diesel if you are doing a lot of towing there is no way a gas motor will keep up with a diesel on a pull. Diesel's were built to pull otherwise they would have put gas motors in semi trucks.
