I'm the one that started the mileage thread. The trucks computer showed me the actual mileage I was getting was 23-24 (at first). However this was on a straight stretch of road. The average mpg was in the 12-15 mpg range.
When I figured up the actual mileage by taking the miles and dividing that by the number of gallons, it gave me the actual mileage as close as I could figure.
No, I wasn't happy because I didn't get the 23-24. However, I soon realized that no road is going to be forever straight. Up/down hills, mountains, head winds, etc. So now I'm content with the 15 or 16 mpg his 1 ton is getting.
But due to the other problems I have with this new 1 ton, the dealer went out of his way to trade straight across, taking my 1 ton and now putting me into a 2500 Diesel. And I came out ahead money wise and with options.
This new truck is not going to be my DD, I bought it to pull my travel trailer, haul motorcycles in an enclosed trailer, etc. Mileage? I really don't care at this point. I will get what I get and be happy knowing it will pull what I want, when I want.
I have also owned four (4) 2013 1/2 ton (Hemi's). Did I get the mileage it stated I should? No!
I'm now on my fourth (4th) Jeep ~ this last one is a 2014 4 door. Am I getting the mileage it said I would? No!
When you buy a new truck or car and see the window sticker saying it will get XX mpg, that is based on running the vehicles on a track for the most part. Yes, they do test drive some across the US or different States. And if you read those reports they will indicate that they did not get the mileage as it was posted.
Yes, you can CIA it, chip it and do other things to get better mileage but for the most part, the money could just be spent on buying fuel for it.
The engineers who design and build these vehicles do so under strict EPA laws so what you may have got 10 or 15 years ago for mileage is never going to happen again.
Leave the engines stock, use the vehicle for what it was built for and be content with the mileage you are gettting.
Finally, take a real hard look at your driving habits, in town/out of town, wind conditions, cold/hot weather, tire size, tire "pressure", etc. All those have to be taken into consideration. You get better mileage if you live at sea level vs living at 4,000' ~ idle time, stop and go traffic. Most window stickers will say you will get an "average" mpg. Keep your engine tuned to the manufactures spec's ~ clean fuel filters, run synthetic oil if you can. May not increase your mpg but sure helps all internal engine parts and the warm up time during winter months is a lot shorter.
My new 2500 will be here in a few days. Mods? Nope, only exterior ones and even those can create air drag.
Just enjoy your vehicles. Life is just to damn short to worry about the price of fuel. Either you can afford it or you find a vehicle that gets more mpg or you stay home. Good luck either way.