Bingo: the lower engine RPM washes out the tread inefficiencies of the larger tire. I'm glad you did this test.

Awesome video, have the same van but the NA engine and consistently get about 18 mpg. Was wondering how the larger tires would affect it so now i know. In my opinion whats killing your mpg is that roof rack acting like a parachute. Keep up the interesting and informative videos! 👍

Great analysis! Awesome van! We have same van (not nearly as cool) and we did notice a loss of MPG at speeds over 65 MPH and it progressively gets worse as you approach 80 mph (we went from Vanco stock 255 75 16) . Our van is a medium roof, but the tires gaves us almost 1.5" lift as it now barely fits in our garage. When our van tires were brand new our speedometer was off by 5 miles (6 at over 67 mph according to GPS). Our van is a 2017 and we get an average of 15/16 mixed city/hwy. We keep our speeds under 65 MPH and try to stay around 50 MPH on lonely roads and we can get up to 19 MPG (I GPS from gas station to gas station and use the miles driven/gallons pumped). Thanks again!!!!

Great tips, as always. Thanks Joe n Kait :)

Thank you for another awesome video guys! 😎🤙🏻🤙🏻

Great video , very informative

Been watching you all for sometime, and appreciate the content. Thank you.

looking forward to the results with the stock tires/wheels after your drive to Storyteller land. Thanks for the video!

i drive an f150 with the coyote engine, about 900 pounds of aftermarket stuff (winch, bumpers, crane, camper top) i need for work. i replaced the stock firestones with 33" ko2's inflated to 50 psi because i kept puncturing the sidewalls of the firestones when driving out in the paddock. you people all hate me because on the freeway im the guy doing 45-50 mph in the right lane. if i never leave the farm, my mileage is 16.5 give or take .2 mpg. if i spend half my time on the freeway, 17.2 ish. if i spend a whole tank on the freeway 18.5. towing a trailer of any weight drops it back to 17.2ish. if you want to save fuel, you'd be better served to simply drive slower. it saves a lot of money and costs you a little time but its up to you which is more important.

Very interesting and I look forward to the next installment. There are 2 other questions I hope you answer. 1) how does each set of tire differ in handling, and road noise; interstate, 2 lane highway and off highway driving. I’ve been debating for a while if I want a more aggressive tire. I assume there is a lift on your van, was there any sheet metal removal in order to accommodate the larger tires?

I think you experimental design was right on (same pump, exact same route at the same speeds). Your comparison numbers are what I would expect based on similar comparisons made over the years in my vehicles. I would expect larger wheels with the same tread design to be equal. And I suspect that the lower MPG for your KO2s might be a result of the more open tread pattern and higher rolling resistance. (There are alot of us Dave Johnsons ;-))

a very good video info for us ... thanks

Basic math. The taller tire has made your gear ratio a highway ratio in the name of ground clearance so its harder on the engine. (think of a 10 speed bike that works the easiest in 4th gear aka factory tire circumference ...the bigger tires make it pedal and work like its in 5th gear all the time instead of 4th) The smaller tire keeps the engine at factory set specs for rear end ratio and living in the engines power band....of course air pressure and width will also have an effect. Bottom line is that you get better off road clearance with the taller tires but better response and power especially fully loaded or towing up hills with the factory smaller tires. Your choice. So fully load up with groceries and water and toys and maybe even a small trailer with a motorcycle and run the test again and you will see the smaller tires shine...especially going uphills.

Good Reviews and really helpful.

I really appreciate the work you have put into doing this. I drive a Jeep and put the factory size while being more off road aggressive, so this will give me a point of reference. Thumb up for this.

3 factors (minor) that you didn’t mention are tire and wheel weight, width, and the fact that the aftermarket wheels lift the van creating slightly more wind resistance. I have an Escape with 2.0 eco boost with a small lift and upsized Wranglers and the biggest difference is IN MY HEAD as the display shows average mpg about 10% lower than it used to. Of course I didn’t recalibrate Speedo so makes perfect sense. I also notice a little wind noise from under the front end now and suspect the air under the car is more turbulent.

The larger tyres will up your gear ratio, it will slow down your acceleration and use more fuel to do that but once your up to speed you will use less fuel, the lower RPM is the confirmation of this. The KO's are the best compromise for on/off road and last a very long time so they save you money there

Thanks for that information

Interesting video. Thx for sharing

I suspect that tire size is going to have a fairly limited effect on your fuel economy. Larger tires require more torque to turn to provide acceleration and maintain speed against wind resistance. Since your transmission has not changed (and the engineers have engineered your car for a specific tire size) you will consume more fuel to achieve the same acceleration and fight any forces that are trying to slow down the car (wind resistance, road friction, gravity). This is a net negative. But, larger tires will run the engine at a lower rpm on the freeway. This is a net positive. Finally, having an aggressive tread will result in more of your fuel being turned into tire heat vs. forward motion. Once again, a net negative. These might cancel each other out depending on your driving style and where you are going. But... all of that is probably swamped by wind resistance. With a large, fairly un-aerodynamic shape, most of your fuel is burned fighting the wind. When that is the case, the slight difference that you would experience from the bigger or smaller tires would become a tiny fraction of the overall fuel consumption. Consider an extremely efficient car (like, say, an Aptera). Since this car is very aerodynamic, a smaller percentage of its fuel consumption is used to fight wind resistance. That means any factors that affect OTHER aspects of its fuel consumption (like road friction or acceleration or fighting gravity) will have a proportionally larger affect on its overall efficiency. So tires might actually change these numbers a fair bit. Since a van is essentially a giant brick trying to move through the air, a much larger percentage of its energy is used up fighting wind resistance (which goes up as the square of speed, so doubling your speed will result in a 4x increase in resistance). That means the percentage that is used in ways that your tires have an effect on (acceleration, rolling resistance, etc.) will have less of a proportional effect. BUT... One other thing to keep in mind is that the way we think about fuel economy in North America is kind of backwards. We think of it in terms of miles per gallon, which hides proper comparisons behind a non-intuitive way of looking at the numbers. Say you have a truck that gets 10 mpg and a car that gets 90 mpg. If you had the option of replacing the truck with another truck that gets 20 mpg OR replacing the car with another car that gets 100 mpg... you should replace the truck, even though both vehicles are improving on their predecessor by 10 mpg. The reason is if you replace the truck, you will use 50% less fuel (for the same distance travelled). If you replace the car, you will only use 10% less fuel. You have to think of it in terms of percentages, not in terms of mpg improvements. So IF you find out that smaller tires actually DO improve your mileage by 1 mpg (just to pull a number out of a hat) you have to convert that to a percentage to find out if it is useful or not. 1 mpg gain for a 14 mpg car is roughly 7% better fuel economy. Not bad if you can make that work.

Interesting and different from my experience with over sized tires. I’d compute distance with a gps for accuracy and bump that highway speed up to 75. Unless ya really take it easy through Kansas ha! Those motors will roll at 90 effortlessly. Great test and anxious to see the “real world” results. Thanks!

Answer is already available by looking at electric cars that offer multiple tire sizes. Ranges are lowered with the larger tires. It’s all the same physics regardless of whether your fuel is electrons or petrol. This is only true within a reasonable range - get too tiny on the wheel size and other problems occur.

That seat belt cover is like snuggling up with Chewbacca every time you drive. Thanks for doing this video. I am surprised too. I thought for sure you would get 1-2 mpg better. Can’t wait to hear how the long term testing does.

How was the ride? That would be an interesting comparison. Quite a challenge to set up criteria. I would think that a narrower tire would get better gas milage considering less friction and resistance.

Nice to have you do this comparison. I suspect there can be quite high variability in pump shut-off, especially with a few gallon test. Good to follow-up with a long distance test. I wonder if you can share more on the likes/dislikes of a 4x4 B-class over the 4x4 truck camper. I imagine comfort, overall room, parking, driving and access while driving are big factors. Off-road capability may be similar? Your ranking of these would be interesting.

Great Job Joe! Yes, I would have thought the tires made more of a difference. Very interesting video. Looking forward to seeing the trip to Alabama! Also nice cameo clip of Kait!

Can’t wait for the results 🍺🌮✌️ looking at an Ekko this fall 🐾👣✌️

Small test loops cause big variances. The TFL channel guys do the same thing. It's hard to get the true numbers until you can average out a few tanks. Interested to see how it works out. Staying east of the Rockies will have a big impact on your pocketbook if that's what you are concerned about.

You can use an OBD tool to see actual real time fuel economy. The tool and associated software can see how much fuel is going through the injectors. The Everlanders use a similar device but I can't remember the brand

Interesting Result!!!

Having a campervan that came with KO2s when I bought it, I have wondered about this. KO2s are great, but at what cost. It will be interesting to see what your long term experiences with each are.

Would be interesting to see a video explaining The rationale of switching back to a van and how that compares with the reasoning from before with the switch from the van to a truck camper.

Very interesting!

From your video a month ago, you were getting 12mpg. Now you are improved to 14+mpg. Soon, it’ll be 15, 16, and 17mpg. As my Transit Ecoboost engine broke in, exact same numbers. There seemed to be a more pronounced increase after the first oil change. Likely the break-in oil from the factory is thicker. I still have pretty low mileage on my van, but I just got over 17mpg on two consecutive round trips from Santa Cruz to the Sierra Nevada mountains and back (twice, to be redundant). Frankly, I was very concerned at 12mpg when I first got the van. At 16mpg, I felt relieved. Now at 17mpg, it’s not bad at all. (Makes me pleased I didn’t spend for the diesel Sprinter.) I’m not sure I’ll get to 18mpg or even 19mpg, but that would be fantastic!!! As you know, gasoline here in California is pretty expensive, and it hasn’t come down from the peak hardly at all (contrary to what the media is reporting about -$1 for the national average). Anyway, be patient and I expect you’ll be rewarded. BTW, I ordered my Transit with the 31 gallon tank, and that is a nice feature. The extra range makes it easier to buy gas at lower priced stations.

It depends on the application of the vehicle and if the mpg lost is worth it. I have had bigger tires on a vehicle - it not only cut down on mpg but it wore out the suspension quicker (even with the modifications done by a professional) and the tires cupped. My current truck was sent out from the factory off road ready.

Really interesting test. Unlike you I couldn’t care less what the tires look like, but if the better off road tires have the same or better mileage it’s a no brainer. Can’t wait to see your next video.

Makes me appreciate our 2WD van, with its 18-20 mpg.

Well, that was a surprise! I'm now getting 13.3 driving conservatively, which is all I expected. I can imagine interstate driving at +70mph would drop the mileage significantly. Thanks for doing this for us LT'ers, Kait and Joe. Very nicely done.

Thx sharing

I agree with other sentiments that is surprising. I know with my old 2003 TDI wagon, I would see a 2-3 MPG drop when I switched from OEM size winter tires (195/65-15) to my larger and slightly heavier summer tires (205/50-16).

This was a great test, Joe! So much work to change out the tires! You are so handy, wow. I think this test was very useful to every single RV owner. We all wonder if tires make a big difference and as you showed, the larger ones are minimally higher but way more functional. I wonder if the tires count as RV max weight limit or are exempt? The bigger tires certainly carry more load. That is great. Nice to see you both again! Hi Kait!

Very interesting.

Someone researching vans options, 14.3 mpg. I'll keep my diesel truck. Thank you for the real video.

Good comparison. Thank you. We have a 2022 Transit AWD, HR, 3.5 Eco, currently with the stock tires, but interested in going to a larger size. So far we're averaging around 16 mpg's. We have a roof rack with a couple solar panels and a Maxxair fan on top. Still building out the inside. Naturally, we'd like to have better, but I'm happy with 16. What kind of air pressure are you using in your stock tires?

Thank you for this video. I also have Ford Transit 350 without ecoboost. I want to get the larger tires but I worried about the gas mileage and the noise. With the factory tires and rims I am getting 13.9 to 14.2 MPG. I wonder if the lift makes a difference?

This was an interesting experiment. Looking forward to the trip. I hope Story Tellers tires make the cut because they do look so much better.⛽

I hope that you guys get around to the all-terrain tires 🥰a whole lot more than the unattractive-looking factory ones!🙄Enjoy your trip,guys!🤗🏞

It does change the drag coefficient and yes it does affect gas mileage. Says Tesla and Aptera who both have done extensive testing. However you don’t wish to get stuck so It may be worth it depending on how rough the places you go.

Surprised the difference wasn’t greater but it might get with wear and distance on the factory tires. Those bigger tires with that rim are beasty looking though. Looking forward to what the Birmingham trip reveals.

it is really a give-and-take situation. if you're rolling down a straight flat highway with constant velocity, your big tires will really shine. the bigger tires will cause the engine to work less to keep the same speed. however with each acceleration (stops and starts) it's gonna cut into that advantage greatly. also steeper grade hills will kill any advantage of the big tires.

It's my understanding that a full build-out on any of the high-roof vans will only result in about 13-15 mpg.

I have a f150, for the second set, I bought Michelin LTX. 275-18-65. Great tire. $280 each. Forscan can get you programmed for tire size matching to the speedo

there's a lot of research into this with regard to cycling. the main factors involved in addition to solely distance per revolution are rolling resistance and rotational mass. the more rolling resistance and rotational mass, the harder the engine needs to work to complete one revolution. likewise, a larger tire radius means more distance traveled per revolution. if you can reduce the rolling resistance and rotational mass, you should gain MPG, but to beat the previous wheels, it would have to equal or better the rotational mass and rolling resistance of the smaller wheel while maintaining the larger tire radius. doing this would sacrifice some grip in the winter though

It’s a heavy vehicle and 14+ it’s not too bad. Thanks for the test.

I like the way you calculated taking into account the odometer calibration. I know that if you don't take that into account the mileage looks worse than it really is. With these vans, I bet the biggest thing affecting mileage is going to be the wind resistance of the van, then the weight, then the driving style, then the tires (diameter, weight and tread design).

Really enjoyed the video, especially when you pointed out you used a google map of 45 miles. The odometer would change actual miles per tire. I got a new RAM and the dealer put on a front level and firestone destination 35 12.5 r20, and the truck should have 275/55 r20. They look great, smooth enough, not calibrated so mph, mpg, speedometer shows 40 and gps 44, gears change at speed so are off, and warranty of 70,000 miles is being eaten away faster. Im heading back to the dealer to get the original tires on, even though they will be much cheaper.

Two thoughts 💭 1. Wind! By any chance, do you know if wind changed? Even 5mph tailwind change into headwind is enough to cause a 2mpg increase for me. 2. Lower RPM! Like you mentioned it change from 1700 to 1900. Could slightly affect your mpg too; although not as much as I would expect from headwind/tail wind.

Bummer. I hadn't switched tires, thinking I was gaining MPG. Now I have to buy KO2s, lol. Can't wait for your 800mi report. :)

I have a Ford transit can with standard continental tires...and the big story here is GROUND CLEARANCE. We have been limited in our off road dispersed camping out west with such a poor ground clearance. Any improvement in ground clearance would make our big trips so much better.

The Ford 3.5L Eco-boost is notorious for gas guzzling when you drive the twin turbos… And acceleration or in towing. You can help that by avoiding a “lead-foot”!

To save a lot of gaz... slowdown on the highway. 57 to 60 max. It will help a lot !

Good Content! What seats are those? I have had lower back issues and those look like they would be comfortable!

Great vid, the factory tires would had faired out much better in city driving due to the stop and go. But that is not really your gig on a every day bases. But Hwy & rual driving a larger circumference may actually fair better. As it did with us. My GMC 1500 was running on 18's with a higher wall tire making for basically a 23inch circumference. I changed out to light 20" rim same weight as stock oem's that came with truck. New rims & tires total circumference 25inch a simple 2inch and i picked up a high gain of 1.5 mpg's better. And for dense city driving due to my work in real estate a Loss of 1/4 of a mile to a 1/2 mile per gallon. Now the big numbers while towing our 26ft camper. A better gain of 1.5 mile gain on the larger rims. Where as the oem 18 inch no difference. Now if you went with a circumference of 33-34 inch with a better hwy tire. I almost guarantee you have batter MPG's and off road the larger tire would scale better anyway then the OEM on the Ford Transit.

I really enjoy facts! You accounted for the different speedo measurements (and subsequent miles). Looking forward to more data because, for 1/4 MPG, I would stick with the big tires…

Thank you so much for making this video. I do like fat and bigger tires on my vehicles and I trully wanted to get a more scientific approach on the gas mileage. Best regards!!

One of the errors made by most people is that unless you have corrected the speedometer for a larger tire, any onboard mileage computer will be in error. Most of those systems are sensing axle rotations based on how fast the transmission is turning, so with a larger circumference you are actually traveling farther for each tire rotation. That means your speedometer reads low, your odometer reads low, and the computed mileage reads low. You need to drive a known distance using mile markers on the side of the road, and then replace the fuel to see what you used in order to figure it out accurately. Or, get the speedometer corrected. Running a larger diameter tire effectively puts you into a higher gear, so you'll suck down a little more fuel trying to get going, and do a little better once you get up to speed, all other things being equal. Once you start adding aggressive tread patterns and wider footprints the rolling resistance gets worse.

Surprised me too, Joe. I know on my Tacoma, when I went to the larger KO 2's, I lost about1-1.5mpg. And that is going with the largest KO 2 I could put on the factory rims. I also added a 2: lift. Now I'm wondering if it is the lift that reduced the mpg, not the tires. I do know the truck is more sluggish with the KO 2's, but, it's a Tacoma. They are always sluggish.

That larger tire is like a lower gear using less rpm's. On a relatively flat drive it should help. You'd think a lot of starting and stopping and chill climbing the increased unsprung weight may make more of a difference, that's my hypothesis anyway lol

Love the Wookie style seatbelt...

Interesting!

Because the reduced final drive ratio with bigger tires (lower numerical ratio) the engine also has to work harder on acceleration.

It is impossible to account for effect of the wind/air resistance in the real outdoors. When towing against the wind vs with the wind our mpgs vary from as little as 9.5 mpgs and as much as 12 mpgs (towing a trailer so yes a huge front area but still similar 20% effect can be a factor for the van) over flat Saskatchewan/Manitoba roads. Higher profile of the van (on larger diameter tires will also play a factor but that would go to support the factory tires as more fuel efficient in this experiment. I'm looking forward to the long term results :).

Hey Joe and Kait! Love this video! I've been thinking about the numbers and think you just need a bigger sample size. So glad to see the factor of mileage distance taken into account, and The variability of when the back-sensor on the pump "clicks off" is quite wide. A difference of half a gallon can be pretty big in the math on this and I get the sense that's what's going on. So glad to see the factor of mileage distance taken into account..Maybe a full tank on each and calculate using a standardized, single measurement for distance like a GPS unit? I also want to add I think even a little difference in driver attitude can make a HUGE difference in how efficient your car is.. Driving with just a little more acceleration...braking harder vs coasting.. Again - great video and fantastic content/topic. Keep up the good work! Rob and Quincy

I just put the black rhinos and ko2 on my awd transit..I love your seats could I ask if u could measure from the floor on the side and front of the seat..cause im getting a set of seats in ya color and u told me you got the amazon set swivels and I got the ford swivels and there not compatible but I have to transfer from my wheelchair to the drivers seat..and I got to get it right the first time so Im not too short or too high..im finishing my van build so I have it ready for chat.tn expo..were getting a spot to show off my wheelchair accessible build and his van building shop.bn loving your journey

You will get some rolling resistance from the K02s versus stock.

With a big tire you'll get better gas mileage on a very flat surface. But that same tire on hills a mountains actually will stress the suspension but mostly the drive train.

What is levelling the mpg of both tires is your vehicle. It is a large vehicle with terrible aerodynamics. It is a heavy vehicle with lots of add-ons with your travel package. Even though the smaller tires would mean lower flywheel inertia to accelerate and stop, they were spinning faster. The larger tires had more flywheel inertia but were turning lees per mile. One of the biggest things people forget is that when you touch the accelerator pedal you are instantly commanding the vehicle to respond. Remember, I said instantly and every little input from your right foot has a detrimental effect on economy. Perhaps finding a freeway where you can use the cruise control effectively to control the inputs will help. There are many tires out there specifically designed for fuel economy but do so at a loss for other things such as ride and traction in poor traction conditions. Maybe look at it in a different way. You have many cup holders and maybe that's all that matters.

I think odometers work by counting wheel rotations. So, the larger tire would need less rotations to cover the same distance as the smaller tire. Making it appear to not go as far, and therefore appear to use more gas :)

What is the cost difference between the 4 big tires and rims , compared to the 4 factory tires and rims ? Do you carry a spare tire ? Is it a big tire or factory tire . If you blowout a tire while out on a trip , which tire will be easier to locate and replace ?

I don't know if it has been said, but there is going to be a noticeable difference in engine RPM at the same speed with the different size tires. Once you correct for the change in odometer it very well could be that the gap between the two tires gets smaller the longer you ride at speed. This effect will be countered by the additional torque needed to accelerate however so it wouldn't surprise me to see a widening difference of "city" mileage. I had a 4cyl Jeep Wrangler when I was a teenager and when I put on 33" tires it actually increased my MPG due to this effect. I have a MODE LT as well and I can tell however that the worst hit to MPG is the roof deck and ladder... Plus.... the BFGs just look too dang good to take off...haha

I am surprised you didn't get a little better mileage. I have a Pleasureway Ontour 2.2 that is built on the larger Ford Transit with dual tires. On our recent trip of over 4,000 miles to Idaho and Montana from San Diego we averaged 16.1 mpg. On a shorter trip where I was either going up a mountain to 6,000 feet and back down I got 14.5 mpg with my odometer saying only 11.8 mpg at the highest point on the mountain. (I have solar panels on the roof, the A/C and two electric bikes on the back. I drive with full fresh water tank.)

If you account for air drag, rolling resistance, pavement temperature and any other variables that could affect the outcome, both tires give the same fuel efficiency.

Yes.

Did you weight the 2 tire/wheel combinations to see if there is a significant difference. Could be another factor.

Thanks! What size tire are ko 255 70 16? Or 245 75 16? Thanks! Nice driver chair too

I wonder about the factory gear ratio. It probably was not expected to be a RV. There used to be after market w/ overdrive final drive gear ratio. They were expensive though. Another option would be to add electric motors for accel assist and regen on hills.

What are the respective tire sizes? I'm not planning on doing much offroading will swap to less aggressive tires like Michelin Defenders on the LT I'm getting.

Also depends on the camping gear load full water etc

Weight difference of wheel + tire and rolling resistance of the tire are also important.

I too have the Storyteller Mode LT. It came with 21 gal of water, we drove it home and got 9.9 mpg mostly freeway and highway. Sandy OR to Astoria OR. We were disappointed to say the least. Were your water tanks full, half full? Weight makes a difference. Hopefully it gets better.

Did you change the odometer computer setting to speed correct for the larger tires?

yes and tread pattern....from lots of experience . 1 car i went from MT to AT and saved 7 mpg , i put slightly oversize AT on a van and lost 5 mpg ( maybe the efficiency of the particular vehicle makes a difference smaller engine may have to work harder ? )

Get the tiresizer app, it will tell you exactly how many turns per mile each tire needs. Example: If the big tire would show 10% less revs per mile and show 3% more gallons per distance, that would mean it makes 7% better MPG with the big tire.

I know a few years ago when I went from factory 4 tires on a 2004 E350 to 1 size larger More aggressive off road tires my mileage was destroyed.

Great Video Joe. We here in Germany drive a Class C Motorhome built by Hymer and have switched from 225 to 245 tires. No difference in fuel consumption . The best way to reduce fuel consumption is by reducing the size of the engine. Our 2022 Mercedes Sprinter with AT KO2 and an overall weight of 4500kg gives us more than 21 mpg in average. OK, it is a 2.0 Liter Diesel engine with "only" 170 hp. But it takes us everywhere we want. Downsizing is the key, I think. Keep up your great work on KZfaq. Dirk

The lower engine RPM on the larger tires will give you a better MPG or similar with the factory wheel/tires. I had the same result with mine Jeep wranger Unlimited Rubicon with stock wheels/ tires 32” and 37” wheels/tires….. 🤪👍💪greetings from the Netherlands

The aftermarket wheels and tires will do fewer revolutions per mile vs the smaller factory wheels and tires. The vehicle's engine revs at lower RPM's with the larger tires, saving fuel. However, the larger wheels and tires are heavier, have more rotating mass, and, a larger contact patch on the road which increases rolling resistance. It may very wheel be, that the advantages and disadvantages of the aftermarket wheels and tires cancel each other out. It will be interesting to see how this plays out with more testing. 🤔

Do you have a spare KO2? Where do you carry it since, as I understand it, the KO2 won't fit underneath. Any ideas on how I can convert the spare tire area to storage?

I noticed that with the factory tire fill up you had less illuminated orange lites ,, was the a c off..

Do you need to change the speedometer/odometer when you change tire size?