Wtfff. At over 65mph I'm showing noticeably lower than you guys have listed.

Could it be due to the size of my wheels? Even with how tall they are they were significalty lighter than the stock 17s or 18 it came with. Gotta say I'm a little worried now

 

Are these numbers in the mid-high teens hand caculated or the stupid mpg calculator dic?

 

I've checked it on trips to upstate new York (uphill @75-80mph) 18mpg. Round town depending on my mood I avg 12-14. I have gotten 420miles out of a tank but I didnt fill up Afterwards so I didn't get to check it. Yes I'm a $25 fuel stop unless I'm going to make a longer trip, as a rule I hang in the last quarter of the tank. That lasts about a week I only live 4 miles from work. I have fuel gauge to trip watched and I can hit around 130miles on the 1st quarter tank on the first stage of my new York run.

 

Hand calculated here.

 

Hand calculated. My 05 was a mid to high teens truck before I ruined it.

 

I used to get low 12's-15MPG (hand calculated and in US gallons) but now I can get 14-16MPG.

I noticed my 2500HD got better mileage If I drove it hard until it got to 3rd gear and let it cruise from that point on. I get more frightened looks from pedestrians, but the people around my area are mostly idiots and easily frightened like sheep.