Mileage is not good on the Tundra whether you have the SC or not. Better with it when towing than without as power is so good that holding speed limit up any grade so far up to 6-7% is easy in 4th gear. As mentioned my trailer GVW is only 7500 and I rarely run with full fresh so my guesses that I'm maxed at 7000. If anybody tells you the Tundra is good on fuel, they are being dishonest but I still think it's a great value to have my house on wheels behind me. I drive a 2013 F150 5ltr footwork and have driven 125,000km in 24 months and that truck is incredible on gas on the hwy and not bad in town butwould not compare it with the Tundra. And the power adder. The Ford is good for 4-5000 lbs then shows its shortcomings whereas the Toyota doesn't show these shortcomings with our TT whatsoever. I'm a Composites raw materials seller and supply to many RV manufacturers and have MANYcustomers and guys willing to share good truck stories. The Ecoboost does great pulling especially in altitudes but gets thirsty also when under constant load. Truth is they all do. Knowing that I'm at the age where I wanted to spoil myself I pay the gas bill and thoroughly enjoy the hundred and 123 extra HP and 149ft lbs extra torque gain over stock. When I talked to the Toyota dealership about the SC install they advised that when damage occurred to SC trucks, other evidence existed that the trucks were used extensively for racing or owners were not happy with 504 hp and actually added other things like under drive pullies etc... 504 is enough for me but I use my truck for pulling, rarely to never for racing. Ok maybe just a couple times!