MPG drop with lift & tires

[dylanc]

Im in the process picking out a 2-3 inch lift and some 265/70R17 tires, and possibly adding wheel spacers.

Im just wondering what other users with similar setups noticed regarding drop in in fuel efficiency. I noticed one user with 285 mud terrains only noticed a ~0.3 mpg drop, while others with very mild lifts reported up to 2 mpg drop. Im sure some of these mpg numbers are corrected and others arent. So if you have a lift, how about shouting out the size of your lift, size of your tires, and the efficiency drop you noticed. Also mention if this is corrected for the increased tire circumference or not (increasing tire size causes speedo, odo, and mpg to display lower than they actually are). Any other info would be great too, like if it affected your street more than your highway mileage etc. Thanks everybody!

:biggrin2:

 

[dheeter]

It will depend mostly on the weight of the tires. I have 33" toyo mud terrains that weigh over 60 lb. each. With those tires a 3" lift and 18" wheels I get around 17-18 mpg. I got 20-21 mpg with everything stock. I correct my milage for mpg calculations by multiplying my trip milage by the percent increase of the tires circumfrence.

 

[boston_kevin]

I think a lot also depends on driving conditions/climate, etc. I upgraded to BFG A/T KOs 265/70R17 and noticed a slight drop, but in the winter my gas mileage drops anyway. I think this is due to the oxygenation of the fuel in Massachusetts and the denser, colder air to push through. I have a 2/1 CF lift and keep the tires around 38 psi.

 

[03_4x4Runner]

I have a 2003 with the V8 and 4x4. I used to be able to get 19 -20 mpg stock best case highway driving. After Daystar 2.5 lift and BFG all terrain 265x70x17 tires I am luckcy to get 17 - 18 mpg highway. This is mostly Arizona mountain driving so there is a lot of hills to climb. There was a slight power and braking lose with the bigger tires. I run 36 psi in the new tires verses 32 in the oem tires. On a trip this summer of approx. 600 miles I averaged 15.8 for the whole trip. This included highway driving (75-80 mph)
city driving in Flagstaff Az and several days of off roading. The highway driving was not easy as it involved a lot of mountain driving and it really worked the engine to maintain highway speeds at times. Definatelly hurt the mileage when kicking out of overdrive to keep up to speed on long steep grades. If I did not off road I would rather have it stock but since I do off road the extra clearance and tougher tires make it worth while. Any time you add taller, heavier tires and put it up in the air with a lift you will hurt gas mileage.

 

[dylanc]

After Daystar 2.5 lift and BFG all terrain 265x70x17 tires I am luckcy to get 17 - 18 mpg highway.

Is this mileage corrected for the larger tires?

 

[vbhosehumper]

I have a 2003 with the V8 and 4x4. I used to be able to get 19 -20 mpg stock best case highway driving. After Daystar 2.5 lift and BFG all terrain 265x70x17 tires I am luckcy to get 17 - 18 mpg highway. This is mostly Arizona mountain driving so there is a lot of hills to climb. There was a slight power and braking lose with the bigger tires. I run 36 psi in the new tires verses 32 in the oem tires. On a trip this summer of approx. 600 miles I averaged 15.8 for the whole trip. This included highway driving (75-80 mph)
city driving in Flagstaff Az and several days of off roading. The highway driving was not easy as it involved a lot of mountain driving and it really worked the engine to maintain highway speeds at times. Definatelly hurt the mileage when kicking out of overdrive to keep up to speed on long steep grades. If I did not off road I would rather have it stock but since I do off road the extra clearance and tougher tires make it worth while. Any time you add taller, heavier tires and put it up in the air with a lift you will hurt gas mileage.

I have basically have the same setup with exactly the same results. I average about 15.5 mpg (corrected for larger tires) with 80% city driving on flat terrain. I read people on this forum getting 17-18 city with larger tires and lift, which is frustrating to me because it leads me to think I have a maintenence issue with my '03. I recently averaged 17.6 miles(95% highway) on a trip to Myrtle Beach. That just didn't seem right. BTW, all mileage calculated miles divided by gallons needed to fill. The dash computer is waaaaay too optimistic by at least 2 mpg's.

 

[dylanc]

I have basically have the same setup with exactly the same results. I average about 15.5 mpg (corrected for larger tires) with 80% city driving on flat terrain. I read people on this forum getting 17-18 city with larger tires and lift, which is frustrating to me because it leads me to think I have a maintenence issue with my '03. I recently averaged 17.6 miles(95% highway) on a trip to Myrtle Beach. That just didn't seem right. BTW, all mileage calculated miles divided by gallons needed to fill. The dash computer is waaaaay too optimistic by at least 2 mpg's.

You bring up a good point in that the dash computer is too optomistic in that it reports you are getting ~2 more mpg than in actuality. Perhaps the people reporting getting 17-18 city with larger tires/lift are going by the dash computer so they really are getting more like 15-16mpg. I have a stock v6, and my computer reads that I get 16mpg city, 20-21 highway. I know Im not the most conservative city driver, but still, I doubt people with lifts and ~32" AT tires are getting better mileage than me.

It seems that comparing mileage gets complicated considering people with bigger tires could be reporting corrected actual mileage, uncorrected actual mileage, uncorrected computer readout, or corrected computer readout. Im sure all 4 of these options yield different answers that vary by a significant amount.

By the way, you say you are calculating your miles yourself, but are you correcting it for the larger tires? Your larger tires have a larger circumference, so with each rotation the truck actually travels slighty further than before. When you go to calculate your gas mileage, your odometer will show LESS miles than you actually traveled. You need to multiply the trip odometer reading by the percent increase of your tires' circumference.
A 30" tire has a circumference of 94.25".
A 31" tire has a circumference of 97.39"
The 31" tire has a 3.3% increase in circumference, thus you must add 3.3% to your trip odomoter before dividing by gallons of fuel.

Assuming you did not perform this correction, your trip where you calculated getting 17.6 mpg, you were actually getting 18.18 mpg. :biggrin2: Ok so this is assuming stock tire is 30" and you now have a 31" tire. I know those numbers arent right, but I was too lazy to calculate stock tire height and guess what size you have now. But hey, now you know how to correct the mileage.

 

[03_4x4Runner]

Is this mileage corrected for the larger tires?

Yes it is corrected for the larger tires. The miles were all from my handheld gps and actual gallons used on fillup. The display on the dash always shows better mpg and I disregard it.

 

[ffongge]

Last Dec 2007 I changed my stock Bridgestone tires for a new set of BFG LT 265/70 R16 A/T tires. I shortly have noticed a significant drop in MPG from the normal ~21 mpg down to about 18 mpg for my normal combined city street and freeway driving. I also noticed drop from ~22 to 18.5 mpg for freeway driving. I have checked the dash computer reading to my calculated reading and the mpg's are in confirmation. I had the Toyota dealer check this out, and they apparently find no problem with the engine or fuel system.

Do anyone have similar experience with their T4R? What can be done to improve the mpg?

FF

 

[zimm]

I dropped 2mpg by using miles on the odometer vs gallons added to tank. Did not correct for speedo error with the 1" larger tires though, so maybe the difference is a little less. I think most of it is the higher ride height which is more drag. Seems to hurt highway mileage the most, in town, not so much.

 

[dheeter]

Before my mpg computer was really optimistic, but now with the bigger tires, it is fairly accurate. Its within 1 mpg of my corrected calculation. Anyone else have this?

 

[ffongge]

Someone brought up an important point. Since the mpg is computed using the recorded mileage driven, the odometer readings should be properly checked and calibrated before trying to determine the mpg with a given set of tires. The vehicle should be driven between two marked mileage posts on an open straight and level highway and the odometer as well as the speedometer readings checked. Then can anyone accurately check the mpg for a given set of tires (at the set tire pressure).

 

[hammersc]

You bring up a good point in that the dash computer is too optomistic in that it reports you are getting ~2 more mpg than in actuality. Perhaps the people reporting getting 17-18 city with larger tires/lift are going by the dash computer so they really are getting more like 15-16mpg. I have a stock v6, and my computer reads that I get 16mpg city, 20-21 highway. I know Im not the most conservative city driver, but still, I doubt people with lifts and ~32" AT tires are getting better mileage than me.

It seems that comparing mileage gets complicated considering people with bigger tires could be reporting corrected actual mileage, uncorrected actual mileage, uncorrected computer readout, or corrected computer readout. Im sure all 4 of these options yield different answers that vary by a significant amount.

By the way, you say you are calculating your miles yourself, but are you correcting it for the larger tires? Your larger tires have a larger circumference, so with each rotation the truck actually travels slighty further than before. When you go to calculate your gas mileage, your odometer will show LESS miles than you actually traveled. You need to multiply the trip odometer reading by the percent increase of your tires' circumference.
A 30" tire has a circumference of 94.25".
A 31" tire has a circumference of 97.39"
The 31" tire has a 3.3% increase in circumference, thus you must add 3.3% to your trip odomoter before dividing by gallons of fuel.

Assuming you did not perform this correction, your trip where you calculated getting 17.6 mpg, you were actually getting 18.18 mpg. :biggrin2: Ok so this is assuming stock tire is 30" and you now have a 31" tire. I know those numbers arent right, but I was too lazy to calculate stock tire height and guess what size you have now. But hey, now you know how to correct the mileage.

Excellent post. Very helpful - thanks.

 

[Autbond]

I was getting 18.5 on the computer before my lift and tires. I have a 3/2 cornfed spacer lift with 33" Mud Grapplers on 20" wheels and am now averaging 13 on the computer. My speedo has not been adjusted so it is probably not that bad but just putting my response up. Also, the 20" wheels def affect the mileage compared to a 17" wheel

 

[cgardnerma]

You will lose at least 1-3mpg with larger tires and a lift depending on exactly what you do. It varies for everyone because everyone does something slightly different. That said, it is just physics:

- Lift increases frontal area and thus drag. Varies with height.
- Bigger tires increase rotational mass and add weight to vehicle.
- Aggressive tires have greatly increased rolling resistance.

cgardnerma

 

[alex56]

Front : bilstein c475 shocks and 884 coils = 3.2" of lift

Rear : superflex rear coils & 1" spacer / bilstein 5125 shock = 3" of lift

[this creates a great set up! and still gives a little rake, so the backs not saggin!]

Tires: 33" - 285/70/17 cooper discoverer STT's & spidertrax spacers


all together considering this, and a K&N CAI and a flowmaster catback exhaust
my milage is allright, it says 19 hwy but im for sure im not getting that i can watch my gas gauge drop as im on the freeway ! in the city im getting about 16 its probably a little less

all in all good for a runner this modded

were your really gunna loose your milage is the big tires with 265/70/17 tires you should really see no difference until you get some 33"s