One thing to think about is that diesels are getting 25to 26 mpg highway. You will need to get a programmer and play with the different settings to get the best mpg. If you take care of a diesel you should easily get over 400k miles. If you don't get at least 400k miles out of a diesel than you should have bought a duramax
I have not heard of any new diesel getting that kind of mileage. Not Ford, not chevy, and defiantly not the new dodge. 400K is a thing of the past with a diesel. All the emissions crap wears out and is very costly to fix. They put so much power out of such a small package that they do not hold up like they use to. Some of these diesels put out more power than a big rig but in a lot smaller package. Put a programmer on it say goodbye to your warranty. Not saying you can't get 400K out of one but it is not nearly as common or cost effective as it use to be Duramax included.
Your oil changes will cost anywhere from 110-160 bucks depending on where you get it done. Changing your own oil does not void your warranty. It costs me ~65-75 bucks to buy the oil and filter. I have not been to a shop yet that includes topping off DEF with oil change unless you pay extra except the dealership. Trust me number wise it does not work out. Another thing you mention is the truck will sit without being run for extended periods of time, this is the WORST thing for a new style diesel. This allows any water in the fuel tank to emulsify and pass through the fuel system bonded with the diesel fuel. Just a little bit of water at the 24,000 PSI these new trucks run their fuel at will destroy the fuel system and you are looking at a 8-12K repair not covered under warranty. Rust also builds on the tiny moving vanes of the variable geometry turbo making it stick then causing costly repairs.
Buy whatever you want as you have to pay for it but cost wise it is not worth it. Don't buy into this 25mpg thing either unless you are buying a short bed 2wd it just ain't gonna happen period. If you do want one that bad I will sell you mine with 85K on it and buy me a gas burner I'll make you a good deal on it LOL.
