I have experience with a 2008 4WD Crewmax 5.7l and a 2011 4wd Crewmax 5.7l FFV. The 2008 has 80,000+ with the only "broken" part being a corroded battery cable. The OEM batteries corrode the terminals badly. It now has an Interstate battery, problem solved. On 65 mph roads, in warm weather, running 85 octane 10% ethanol gas it averages just under 20 mpg. With the new stretches of 80mph interstate thrown in on a trip it drops to 18mpg. Big surprise, drive faster lose mpg.
It hasn't been babied. We have a 16ft tandem trailer to haul a 4wheeler spray rig, 250 gallons of water and other equipment for field work. It drops the mileage to 16 mpg. A grad student who used and abused the truck one summer told me it will go over 100 mph. Luckily, the dumb ass didn't wreck it. I had some dash lights come on after the last trip this summer. I googled it and determined it was a known emission-AIP issue that Toyota had extended warranty coverage on to 10 years or 150K on. Had fleet take it to the local dealership and they fixed it for free and detailed the truck for any inconvenience it might have caused us.
My personal 2011 only has 23K miles, no issues at all. I put anti-corrosion pads under the battery terminals to prevent a repeat of the 2008's issue. I put LT 10 ply tires on it as I want the safety factor if I get a flat while hauling my small steel 3 horse gooseneck stock trailer. While pulling 3 horses and carrying 3 people and all gear and equipment over the Snowy Range and back to Laramie, I got a little over 13 mpg. That is about the best I could ever do with my old 1982 Chevy 3/4 when it was empty, with a strong tail wind.
The Tundra has been a good truck for me. I really like the Tundra's transmission for towing. It reminds me of the old John Deere tractor Powershift transmission. Just put the truck into tow mode, drop the shift in S mode, and then shift into the gear you want and it does it so smooth you never have to touch the brakes at all. I have a friend with a 2014 Ford Ecoboost. A very nice truck but his hand calculated highway MPG is only 21 and his truck cost $14K more than mine. However, I think that except for lacking heated leather seats his is fully equipped whereas mine is the base model.
