Just got back from Colorado.
Started from home in KC with around 1,000 miles on the odometer. I have removed the front air dam thingies and put on 275/70/18 E-rated Falken Wildpeaks, so I expect a little worse MPG. Was also driving with my XL-sized mountain bike hanging off the back on a 1Up hitch-mounted rack, and probably around 600 pounds worth of luggage and occupants. Cruise set on 80 mph.
Was getting 13.7 mpg on the way to Colorado, according to the carputer. That's way worse than I was expecting. On the way home today, I calculated the last stretch myself and wound up with around 14.2 mpg. Still bad.
Before I changed the tires, the stock tires were getting me around 19.5 mpg in town according to the carputer. I never really checked in-town with the Falkens as I picked them up about a week before I left town, and never checked highway MPG with the original tires because I never took a highway trip with them.
I didn't really buy this Land Cruiser for the MPG savings, as ultimately the price of gas is a drop in the bucket compared to the price of a new car. But where this really plays a factor is in the 18-gallon fuel tank. I was having to stop far more than I would like to refuel. Speaking-of, other commenters are correct: the vehicle's "miles remaining" ticker is way off. Today I refueled once when it said I had 11 miles remaining and only put around 14.5 gallons in.
My hope is that there is something with the powertrain that takes some miles to fully break in. But I'm at almost 3,000 miles now. Surely some heavier and bigger tires didn't put that big of a dent in the MPG?