Newer Tires, Poor gas mileage, what is main cause?

Both sets use Toyo Open Country ATIII C-load tires.
265-75-16 on TRD beadlocks to 265-70-17 on TRD Rock Warriors are 8lbs each heavier which roughly equates to 320lbs of chassis weight.

 

For sure that is good perspective, it’s like a 3 mpg average drop, so it winds up like 350-400$ a year, which isn’t a ton in the grand scheme but it adds up. It’s nice to try to understand what is the actual cause, considering I drive 99% of the time on the highway, is it more the wheels overall diameter or more the tread depth/knobs/road friction? But Sounds like tire weight and some combination of the others. I appreciate your input to help me understand how the tires affect fuel economy!

 

You truly won't know the ramifications for about a year's worth of data. Write down mileage at fill up and next fill up divide the mileage by gallons used. Only truly accurate way.

 

I run a 295/75/16 toyo a/t 3,the truck came factory with 265/70/16. If I go by the computer doing the milage for me I average around 13.5 to 14 mpg. If I measure my milage using a gps for true milage and devide that by gallons I'm getting 15.5 to 16 mpg. You need to have a way to measure true milage after bigger tires or you never get true results.

 

Ya sounds like I need to verify if the dealership calibrated that or use the old fashion method to determine mileage.

 

Not the weight. There are multiple factors and each only hurts fuel mileage slightly, but combined it adds up. The fact that most of the other factors also make the tires heavier is coincidental. If you keep all other factors the same. Same size tire, same tread type etc. and only change from a 40 lb standard tire to a 55 lb LT tire the fuel mileage will remain so close that you'll need to go several digits to the right of a decimal point to measure it.

I've been using both standard P series tires and much heavier E rated tires on trucks and SUV's since the 1970's. I've had both types on multiple vehicles and as long as I stayed with the same size and a similar tread I've never noted any difference in fuel mileage. I have noted some difference in acceleration and ride comfort.

BUT... when you go to a taller tire the engine has to work harder.

Wider tires with more aggressive tread greatly increase rolling resistance. If you're coasting downhill you can see a dramatic difference between tires. This is the biggest culprit. Guys who go tall with skinny pizza cutter tires don't see nearly as much loss of fuel mileage. Especially if you avoid aggressive mud tires.

3-4 PSI difference can make 1-2 MPG difference, keep the tires aired up. Bigger tires ride rougher and lots of guys underinflate them to get a better ride.

The taller tires mess with the accuracy of your odometer meaning you're actually driving a little farther than you think you are and getting a little better MPG than you think. But this isn't a huge factor. If you do the math to get the correct mileage expect about 1/2-1 MPG difference.

 

Yup, i dropped a little bit fuel economy when i went to 265/70 16's a/t tires from the stock 245/75 16's all weather ones. Sill get up to 23 mpg highway. In town is rougher than the stock fuel mileage.

 

2017 sport was getting 19mpg on factory originals, went to Michelin Defenders and now getting 16mpg, around town driving only, not much highway, per the readout thigamajig, seems like a lot

 

Both. No brainer.

 

I have a TRD off-road manual that came with the stock 31" Goodyears and I got about 20mpg with those. I replaced the stock tires a year ago with the same factory 31" size and chose slightly more agressive General Grabber AT2's (not the heavier ATX version). Even with tires being the same size and about the same weight as stock, the more agressive tread has dropped me to about 17 mpg, alone. So yeah, as others said all those factors are definitely having an impact.

 

Good revival.

Not many of these floating around.

 

I know this thread is from last year, but there are no fuel pump recalls on ‘21s. They started fixing them before then, so it wouldn’t make sense for Toyota to keep installing the known faulty ones in their new trucks after they’ve already been correcting the problem in the older ones (more work, more money, more liability).

I’d say it is a 110% chance the dealership did not recalibrate your speedo when they mounted your new tires unless you specifically asked them to. The difference in average MPGs going from stock 31s to 32s is about .5. So if your dash says you’re getting 17.5 average, you’re really getting 18, but the truck’s calculator isn’t that accurate. Whenever I calculate it myself at the pump, my dash always seems to be off by +/- 1 MPG.

 

Nah, tire and wheel weight absolutely play a significant role in fuel mileage. The heavier the tires and wheels are, the more gas the engine uses to get them moving every time you accelerate from a stop and also when going uphill. 15 or so additional lbs. on each corner can easily cost you 1-2 MPGs (not decimals as you say).

 

whoa this is a cool website!

 

Larger diameter tire.
Tires weight more.
More aggressive tread pattern.
And…

 

Technically the larger tire would travel further making less of a revolution that the smaller diameter tire, so its probably the tire itself big that
they weight to much including the wheel weight.

 

Good job, kitten killer.

 

I notice my MPG goes down during colder months and back up during warmer months. This could also be a factor too.

 

Larger wheels will generally have more rotational inertia, even at similar weight, than smaller wheels.

It’s not about weight on the scale, it’s about rotational inertia.

 

I'm always curious about these kinds of numbers. I've tracked every gallon through my truck for almost a year now and I'm at 21.04 MPG average. That's also currently dropping now that I'm on my third tank since installing LT255/75R17 KO2s (C rated) on 4Runner Pro wheels. Before was stock. My first tank was 18.01 MPG and second was 18.09 MPG with mixed highway/city driving and a number of relatively light loads in the bed as I moved across town. I also KDMAX PRO tuned just before the wheels/tires were installed.

Are you tracking your MPG using the onboard computer or continuously calculating based on miles/gallons between fill ups? I ask because numbers seem to vary widely and I'm pretty light on the throttle with the above results.