Just recently lifted and done a few little major mods to my mini tank. I added a fj coil springs on all 4s and blisten 5100s (set @ 2.5 setting) and in the rear. also picked up some new bfg MT 255s.

So my front sits at 23.8'' high and the rear is 22.4" high. So basically the front sits up about an inch higher than the rear.

So before all this i was avg 16-19 mpg consistently. Now i havent even hit 12 yet. All calculations are done by myself, not the in dash calculator.

My question is, 1) am i getting bad mpg because the front is so much higher, causeing a air aerodynamics. if so....

2) raise the rear an inch with a .5 spacer and keep front the same at 23.8...
3) set the front down to the 1.5 notch and loose a little lift.

Would either choice give me (basically) the exact same results? Im trying to sit the higher the better

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You are getting bad mileage because of the tires.

I was getting a consistent, hand calculated 16.25 MPGs on my daily routine all year long. Just put 255/75 mud tire on this month and the next two tanks were in the 14s and this current one is in the 13s.

Taller tires put more mechanical leverage against the engine and make it work harder. That's one reason they use more gas. The other reason is that the tread is more aggressive and has more rolling resistance. The last reason is because the tires are heavier and add more unsprung weight to the vehicle. All of these things destroy fuel economy.

Don't listen to the people who say they upgraded tires and their MPGs didn't change. Those folks are doing math wrong.

I have the same 255's and I have experienced only a 1.5 mpg loss with my 255/75/17 with Icon lift. I like these tires. One of the major reasons I went with this size was not to have a heavy hit on mpg. Glad I got the 255's since I get 18mpg mixed driving. Love the look too!

Maybe the V6 gets better mpg with slightly bigger tires?

Are you guys taking into account the odometer error? With larger than stock tires, you will travel further than what the odometer reads. It won't make a huge difference, but if you're not accounting for this your calculated mpg will be lower than actual. I noticed no loss in mpg with 255/75/17 all terrains (hand calculated and corrected for odometer error), but those BFG's are heavier and more aggressive which will hurt your mileage.

My bet if it is your tires. The 4runner has the aerodynamics of a brick. Raising it up 3" should not help or hinder it.

The rolling resistance the larger tires are more than likely the problem.

My 2006 with the V8 got 18-29 mpg with the factory tires. Since I put 275-70-17's on I am down to 13mpg average. If I drive it nice I can squeeze 15 on the freeway.

You can run the air pressure up to the max pressure listed on your tire. That will help more than anything.

Good luck, Sammy

Yeah, I figured in the odometer error on mine. Stock, mine was 2% fast (per GPS). After the 255/75s she is now around 3% slow (per GPS). So I figured that all in. I'm probably somewhere around 1.75 MPGs lost now... which for the average U.S. driver (myself included) is equivalent to about $30 bucks per month.

You know the old saying... "If you wanna' play, you gotta' pay."

There is a strong possibility that I may be going to ATs and ditching these new MTs in the very near future. I simply don't have as much time to go on the trails as I used to and honestly an AT tire would suit me better.

I agree with all but & mine is lifted also , I think this is because of aerodynamics and why I think the front end is soooo low in an effort to help gas use in suv , another by product of larger vehicles . So for us to have our 4r look pleasing to our eyes we go thru all this & you gotta live with it . Those smarter than me would think being a little nose high it would suffer by having air flow pushing up under as opposed to nose low IMO

What air pressure are you running? You should be around 37-38 psi.

Im glad air pressure was brought up. I have gotten varying answers on what air pressures should be used while on pavement. Some have told me I should stick to what it says on the drivers door tag regardless on what I changed my tires to. (running General Grab AT2'S in LT265 70 R17) and others say go with what the new tire says; although that is max air pressure at 80psi which seems excessive to me.

what is the general consensus or rule of thumb here...

Are you sure your front spring perches aren't on upside down? Looks like way too much lift with the 5100's on the 2.5" setting since you're almost 1.5" higher up front. Or I could just be imagining things...

Read the linked thread. LT need different psi than P.

http://www.toyota-4runner.org/genera...-pressure.html

I think he just has fj coils in the rear without a spacer; that could be why the front is that much higher.

How does one do a speedo correction after installing larger tires?

I'm on stock tires and get 19-20 avg. I'm going to cry if I take a 3-4 gallon hit with a lift and 275/65/18's. I may have to go with 255's to save fuel economy.

I thought the 2.5" setting would just get rid of the rake, while his truck is ~1.5" higher up front.

My 5100's on the 0.85" setting still have quite a bit of rake (stock springs), and I thought the FJ's had about the same amount of rake, just taller.

This is the only way to correct it to my knowledge.

Speedometer correction - Toyota 120 Platforms Forum