This question at this time...is pure speculation because the 2017 F150 with new revised 3.5L EB is not out right now. However, this is still a valid question...IMHO.
So...the question is: How many miles per gallon would I lose if I go with 33" or 35" (equivalent)??

Now...this is all based off the Suggested MPG that FORD claims at 18 city and 23 hwy


Thanks!

biz

 

in order to fit 33" you're going to want to lift the front at least a little. To fit 35" you'll have to go up at least 2". The additional drag plus the heavier weight of the tire is going to contribute a lot more to fuel economy than tire size alone. In my case, a 2" lift and keeping the stock tires resulted in about a 2MPG loss on the highway. On my last truck, same suspension but with a 34" much heavier all-terrain tire, I lost about 3.5 MPG on the highway.

 

Yes...that is correct. I will be planning a ReadyLift 2.25" leveling kit install.

If I lose 3 mpg, that would be acceptable. Going from 23 to 20 is still awesome mileage...IMHO.

djjoshuad -- Thanks for your experience!


biz

 

well I should clarify... my last truck was a Tundra, and it got about 18 MPG hwy in stock form. losing 3.5ish with the lift and tires means about 20% loss. If you translate that percentage to your truck, I would expect somewhere between 4.5 and 5 MPG loss. IMO, if you go up 2.5" and put on some 35" heavy tires, 18 MPG on the hwy would be quite good. I wouldn't be surprised if you hit more like 16, depending on your right foot

 

I went with a 2.25 ReadyLift. Tires spec at 34.3" tall. Before I corrected the speedometer, It looked like I lost 2-3 MPG on average. After speedometer correction my fuel economy is not too far from stock, within 1.5 MPG or so.

The tire I selected resulted in a 10-12% speedometer error, which had a negative impact on percieved MPG. Now the speedometer is correct, but with a 3-5% slow odometer error. This is consistent with the factory speedometer reading fast by the same amount. Now the dash readout for MPG and hand calculation are closer than it was with the factory tires and speedometer setting.

My biggest MPG loss is driving into headwinds at 75 MPH plus speeds. Also, I have notably better MPG at elevations over 4500' using medium grade gasoline. The EB loves climbing mountain roads, rarely down shifting lower than 5th.

 

That is some good positive news JKBrad. Thanks!

The '17 3.5 EB should perform brilliantly here in the ABQ area. We are about 1 mile above sea level (5280 ft) in elevation. Plus...most of the locations I drive in NM...just go UP from there.

Think I might have found my perfect combo in a '17 F150. Will look good, but also still perform.


biz

 

You won't believe the thrust you will feel when you give it just partial throttle on a long grade, even at high elevations. I drove it up to 9000' at Cloudcroft and could easily pass any slower moving traffic. And thats with tires 2.4" taller than stock.

 

My son just put 18" 33's on his from 18" 32.s and went from 21mpg to about 16. He's not a happy camper.

 

^^^^^ Looking cool comes with a price

 

More info on the truck?? Year, engine, gearing, etc.

Did you son also program the ECM with a HyperTech for the new tire size? See post from JKBrad...


biz

 

Your son is in the same situation I am. I went from 265/70/R17 to 275/70R18 and lost about 2.5-3 mpg. My solution is too find a nice looking set of 17'' wheels, and throw the 265/70/R17 on them.

 

The width of those larger tires will kill your mileage worse than the diameter... Then there is rolling resistance to figure into the equation. You switch out highway treat for an all terrain tread - you pay yet another penalty...
Air your tires up to the maximum on the sidewall for the best fuel economy and load carrying capacity.
Lager diameter tires will mess with your overall gearing to a degree - but typically it will be lower RPMs on the highway and may well result in better fuel economy given the same footprint as the previous tires.

 

That is interesting. However, are you sure you lost the 2.5-3 mpg? It really is impossible to tell if you did not re-calibrate the ECM. After all the miles driven will not be proper on the odometer because of the revolutions per mile difference from larger tires. Plus, the transmission will not be shifting at the proper times, because it still thinks the tire size is stock...which could result in poor mpg.

Just a few thoughts here...


biz

 

I'll be interested in seeing what a 17' 3.5 ecoboost does with a set of 35's.