3rd gen mpg. How and why

Live in Denver, on stock suspension and tires, have the added weight of a cap and drawer system (300lbs), 60% highway/40% city and have averaged 19.9 mpg through the first 3900 miles on the truck.

I don't see any reason why those tires should hit the fuel economy that much??? also are you factoring in that the new tires are approximately 3.4% larger so you cannot base it off the trucks computer. this would put your 16 to 16.544 which i know is not huge but it does make a difference.

EDIT: what PSI are you running? that could also help your case

 

instead of driving 70+, 55-65 mph range helps. I also roll into red lights (when cars arent behind me or there are two lanes) This also helps. I've been experimenting. I pick up my baby daughter and she's asleep so I drive slow to maximize her nap time. Ive gotten up to 24 mpg on country roads going 55mph. When I drive normal and not slow I was getting about 21mpg

 

17x9 Fuel Beast wheels with Toyo Open Country AT2's 265/70/17, Icon Stage II. Sliders and some armor.

Get around 15, mixed city and highway. Not hot rodding it, not granny driving. I switched out wheels/tires pretty quick, but I don't remember getting great mileage before that.

I'd be curious to switch out to stockers and run it for a week to see if there is a huge difference.