My 2021 Toyota Tacoma Was Getting 20-22 MPG, But When I Lifted It I Get 15 MPG at 65 MPH And It's Consistently Downshifting Now

Easy fix, change the gear ratio. Rule of thumb you change one thing and be prepared the change others. I own and older pickup with a mix of Toyota parts from 84-2004 lifted and larger tire and have no problems getting 20+ mpg on the highway, but that in it's self wasn't the goal. That wasn't the goal I had with my 50 year old muscle car either so who's really counting when you modify your vehicle.

Lift a truck and put on off road tires and then be surprised mpg drops??

Just regear it. It's not a hard problem.

There is a company local to me here in B.C. that remaps the ECU for just this reason.
I would do some research to see if someone like that is local to you.
Not a Yota owner personally but have had lots of clients and friends with them. Apparently it makes quite the difference on performance. I'd say for the MPG difference you're now seeing it's worth looking into.
FYI with the new ones you will find it shifting much more with the new added gears in the new transmission. A lot of customers aren't used to the new 8 to 10 speed transmissions, and not sure of one manufacturer that has not had issues with theirs (had to do recalls)

Additional air/turbulence under the vehicle may be exacerbating the problem. If high exit angles aren't a requirement there may be aftermarket spoilers available.

There is no escaping increased frontal area when you raise a vehicle. Drag goes up.

Duh... you effectively raised the gear ratio which is already too tall. These gear hunt and feel under powered stock. I run 265s with 5.29 gears and no gear hunting and pulls like a freight train at gvwr. Gotta upgrade function not just looks. I cringe every time I see a lifted tacoma with every bolt on known to man yet no gears or lockers.

My Prius consistently averages over 52 MPG just saying.

With larger overall diameter on the tires, you're actually going faster and farther than the ECU thinks, with every rotation. You gotta do some math for the exact conversion, and you'll definitely have lost some effociency, but you're not as far off the original mileage as you might otherwise think.

The author of this article just proved how mechanically inclined he is.

Another thing happening is the larger tires have a longer rolling distance per revolution. You are now traveling a further distance than the odometer shows. Your actual speed is also higher than the speedometer shows. The gas mileage change may not be as large once you adjust for these differences.

I had my lift and tires on my 2020 Tacoma DCLB done before the OTT tune, got the OTT tune and the MPGs went up by about 5% normal cruising... everyone has different expectations. Manage them accordingly.

My experience with my 2017 Taco double cab, I have 110000 miles on it, is the tires are critical. Larger tires, more aggressive treads, even going from te all season stock tire to a tame M&S Tire changes the fuel economy. Add a lift to that and you probably reduce mpg more.

None of you are mentioning the yaw/g-sensor that the transmission uses to gauge hills for it shifting algorithm. Any time you disconnect the battery it needs reset. If you changed the ride height, it needs reset. My 2018 Tacoma was shifting erratic after a leveling lift and slight tire increase until I reset that and boom! No more excessive downshifts.

Another factor to consider apart from a lift is tires. Bigger tire reduces fuel consumption obviously. Also tire type. I have type e tires on my 2013 Taco. 10 ply because the previous owner had a camper on it. If you’re not hauling or towing with your truck you might consider a C rated 6 ply tire.

You have added LT tires which rotational mass are much heavier than the P tire that the Tacoma is developed with. The automatic is more susceptible to busy shifting than the manual transmission, the only thing you might try to do is put it in manual mode and manage the lockup of the torque converter while in high gear.

I have a 2017 Jeep Patriot, did the same thing- lift kit and big tires and now the auto shifting is irregular and the fuel economy was reduced. Plus I feel a strain on the small 4 cyl engine. Looks great but yeah…

If you haven't already reset the speedo for the larger tires you are getting a completely messed up mileage number. Larger tires also change your final gear ratio which in turn makes your Toyota much less able to pull like it used too,such as accelerate and or climb hills.

Those comments on aftermarket modifications affecting performance including mileage is true in most instances. I have been in the automotive industry for almost 50 years and have dealt with those concerns. Unfortunately I’m not sure if that’s what he is dealing with. I also purchased a 2021 Tacoma TRD and from day 1 and 6 miles on my truck it did the same identical thing. Mileage is about 15 mpg and downshifts all the time, especially with the cruise on.
No modifications have been made! Factory tires, wheels, no special tuning and no lift kit. NOTHING!! I spoke with the dealership and was told that it was normal. Why he was not experiencing anything until now is anyone’s guess. After years as a tech, parts manager and service manager the problem feels like a programming issue to me.

I’ve had 2 prior Tacomas (1992 and 2005), both with manual transmissions, lifted 3” spacer in front, new Alcan leaf springs packs in rear, 31”x10.5 cooper tires (10ply) with TIMBREN overload elastomers, and heavy duty plate steel front and rear number from Ruenel. Yes - 15 mpg was average. And I loved them, went anywhere and everywhere without any problems. I often had to pull my friends Ford and Chevy trucks out of the mud and ditches at hunting camps or when off-roading….. hard to beat the Tacoma! Who cares about 15 mpg…..
Sell the automatic and get a manual transmission. Not sure they make them anymore.

Wow, very great job stating the obvious.

Guess Facebook posts are news now.

265s dude is stuck in stone age. 35+s is the way to go. 9 mpg, chick's, better offroad capability. If you wanted mpg should have got a maverick.