Can this be true? Mileage hit sticking with OEM size on BFG KO3's

[DNazzy’s2025]

As my dad always said… gotta pay to play. Ford engineers design these trucks with every little variable in mind to maximize the MPGs. As soon as you start changing the equation with different tires, lift, etc - you will impact MPG. Like everyone else said: Rotational mass, rolling resistance, drag, and additional friction are all at play when you go from a SL road tire to an all terrain, hybrid, or mud tire. For me personally, I’m willing to take a hit on MPG for a larger and much better looking tire. It all comes down to what your priorities are. If you want maximum MPG or very little impact, I would recommend leaving the truck bone stock.

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[JohngaltinOC]

What’s your tire pressures? Higher tires pressures = a little better economy. 17 mpgs sound like real life efficiency to me.

That does seem rather dramatic. Did the weather change? Do you have winter fuel. How far apart were your tests? Many things can affect fuel mileage. Especially gaining 32 pounds of extra rolling rotational force.

Sorry for delay, wasn't getting notice when someone replied.

I did increase to 40 PSI for that reason when they were mounted.

Seems the consensus here is that it's not all that uncommon for that much mpg loss with the weight increase and aggressive tire tread change. There was no change in size or suspension. I might check alignment as ChatGPt says even a little bit out of true will make a meaningful difference, even if I can't "feel it". Also told me after a few miles of wear the tread will become less resistance than new. Your point about winter fuel is a good one as well, I think last trip was in summer months.

As someone else wisely mentioned it's a truck and it is what it is....

 

[jkosh22]

Sorry for delay, wasn't getting notice when someone replied.

I did increase to 40 PSI for that reason when they were mounted.

Seems the consensus here is that it's not all that uncommon for that much mpg loss with the weight increase and aggressive tire tread change. There was no change in size or suspension. I might check alignment as ChatGPt says even a little bit out of true will make a meaningful difference, even if I can't "feel it". Also told me after a few miles of wear the tread will become less resistance than new. Your point about winter fuel is a good one as well, I think last trip was in summer months.

As someone else wisely mentioned it's a truck and it is what it is....

Yeah it’s very unfortunate losing MPGs when you were getting old numbers. Also to get a true measurement, you should correct or AFE in engineering mode. Or do your own calculations. But it’d be nice if the trucks didn’t lie to us.

 

[JohngaltinOC]

It's not just weight but rolling resistance. Factory tires are chosen for best ride and economy. KO's are the opposite of that. That said, there's something else giving you 5 mpg drop on one trip. Probably wind conditions. You'll need many more miles for a proper comparison.

This was a Vegas run (260 mi one way) and on the way there I had a head wind the whole way and it showed 15.6 mpg (also manually calculated it), so I didn't freak out too bad. On the way back there was a cross wind to slight tail wind and it came out to 17.4 mpg. So I was ignoring the first leg out for that very reason. Good point though!

 

[gp1200r]

I switched from the stock 18 inch rim and Goodyears. To the 18 inch Tremor wheel a litte narrower 7.5 inches versus 8.5 inches on the stock XLT ones. Stayed with stock height versus going to 33 inch tire. Went with Copper Road Plus Trail tires. Hope was to off set the weight of the tire with rim size a little. Plus I like the look. I lost about 2.5 MPG. Hoping to level out around 1.5 MPG loss after winter and they wear a little. They were right around 5 pounds heavier then stock set up. A lot more contact patch on the road. Tire handles great. Getting around in the wet and snow is greatly improved. So like others have said it depends on a lot of thing. Rolling resistance Is a big one. A grippy tire is safer but at the cost of rolling resistance in most cases. Also depends on tire contact patch air pressure so on. My thought is having a tire that is safe for your type of driving is more important then the fuel economy loss. But that’s just me.

 

[Billflangjr]

This is exactly why I’ll stick with highway tires. Aggressive all terrains might look cool, but it would be foolish to suffer the noise, ride and MPG drop when I never go offroad.

Well when you’re off road all the time like I am, you have to put an upgrade tire on your truck. I live in Florida and it’s swamp where I drive in and out of. M/T tires is the only choice I have. Bigger the better. I do stay close to stock size. But I do run 20’s Summer time I run what came my Tremor.

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