Gas mileage WAY down with 265 75 16's?

[1985taylor1925]

I got my 265 75 16 Cooper Discoverers just before making my trip back to WI from WY. These are just over an inch more in diameter than stock 70's (70's are 30.6" and 75's are 31.7"). Thats not a huge difference. Well my highway gas mileage went from 20-21 mpg to 16-17 mpg, which absolutely IS a huge difference. Is that right? I remember last Christmas break averaging around 22 from WY to WI cause its down hill, and plus at lower elevation theres more oxygen. Three weeks ago I averaged 16.5 mpg, with not much weight in the back. Thats ridiculous. And its been consistantly that bad since. So how many of you guys are running the same size tires, and what are you getting for mileage??

 

[PitbullRescuer]

I'd expect to loose some but that's a lot. What brand/model tires did you run before? Are the new ones a lot heavier? Keep in mind too that your speedo at say 65mph with the 70 series isn't as fast as your speedo at 65mph with the 75 series. So at any given indicated speed you're going faster with the taller tires (your speedo will read slower.).

 

[A.Wilson013]

Does Wisconsin switch up their fuel mixture for the winters?

I get 16-18mpg with a rather heavy foot, and a supercharger...

 

[Clemsonfan15]

I went from Greenville to TN which has a lot of elevation change. Somehow I managed ~20 MPG.

Around campus 95% city I get ~15 MPG.

 

[IntoTheVoid]

That is really odd.

I had Pirelli ATR 275/70 16 tires and was getting 20-21 mpg on the hwy. Now I have Cooper STT 285/ 75 16 tires and now I am getting 16-17 mpg...Very strange.

 

[BrianSD_42]

Well my highway gas mileage went from 20-21 mpg to 16-17 mpg, which absolutely IS a huge difference

I have 275 tires (31.5") and I get 16 - 18 MPG.

I have always gotten that amount. I do not have a SC.

As far as people claiming to get 22 consistently .... well unless you have a S/C that should be impossible.

The MPGs on these trucks (non-aspirated) are pretty well mapped out and 22 is far outside the vehicle specs.

:hatsoff:

 

[derekabraham]

I'm getting about 18.5 MPGs (all highway in the summer...) with 285/75/16 KM2s. Perhaps you're not taking into account the fact that the slightly larger tire is throwing your odometer off a bit? Your driving habits could be affecting it as well. Lay off the skinny pedal a bit? Keep it under 2000 RPMs? Just a couple suggestions.



Winter gas could be an issue. I've noticed mine go down a bit as the winter months approached.

 

[4-Ripcord]

The last 3 tanks have all been above 21 mpg. Highway miles (65-70mph) with ethanol free gas and S/C


OP, try a small tune up. Clean the filter, TB, MAF, and reset the EFI fuse. That should help

 

[ALBPM]

I'm getting about 18.5 MPGs (all highway in the summer...) with 285/75/16 KM2s. Perhaps you're not taking into account the fact that the slightly larger tire is throwing your odometer off a bit? Your driving habits could be affecting it as well. Lay off the skinny pedal a bit? Keep it under 2000 RPMs? Just a couple suggestions.

Winter gas could be an issue. I've noticed mine go down a bit as the winter months approached.

There's a 3.4% difference going from a 265/70/16 to a 265/75/16 which is not
enough to justify going from 21-22 down to 16-17 mpg.

Maybe time for a new air filter or tune up.

 

[A.Wilson013]

The last 3 tanks have all been above 21 mpg. Highway miles (65-70mph) with ethanol free gas and S/C


OP, try a small tune up. Clean the filter, TB, MAF, and reset the EFI fuse. That should help

GTFOOH.


My BEST was 21MPG, going 55mph for a complete tank.

 

[RunninInGA]

I have 275 tires (31.5") and I get 16 - 18 MPG.

I have always gotten that amount. I do not have a SC.

As far as people claiming to get 22 consistently .... well unless you have a S/C that should be impossible.

The MPGs on these trucks are pretty well mapped out and 22 is far outside the vehicle specs.

:hatsoff:

I average 21.xx consistently. See:

Date Odometer Reading Gallons (US) $/Gal Total
1 Jan 13, 2012 103,223 mi 15.653 $ 3.359 $ 52.58
2 Jan 9, 2012 102,887 mi 15.618 $ 3.339 $ 52.15
3 Jan 4, 2012 102,549 mi 17.315 $ 3.259 $ 56.43
4 Dec 31, 2011 102,182 mi 16.211 $ 3.159 $ 51.21
5 Dec 26, 2011 101,824 mi 14.397 $ 2.979 $ 42.89
6 Dec 22, 2011 101,519 mi 15.296 $ 2.989 $ 45.72
7 Dec 19, 2011 101,186 mi 15.302 $ 3.059 $ 46.81
8 Dec 14, 2011 100,868 mi 16.423 $ 3.299 $ 54.18
9 Dec 10, 2011 100,519 mi 16.206 $ 3.129 $ 50.71
10 Dec 6, 2011 100,209 mi 15.237 $ 3.179 $ 48.44
__ Fuel Economy: Total Volume: Avg Price: Total Cost:
__ 21.16 MPG 157.658 Gal $ 3.179/Gal $ 501.12

 

[ALBPM]

The last 3 tanks have all been above 21 mpg. Highway miles (65-70mph) with ethanol free gas and S/C


OP, try a small tune up. Clean the filter, TB, MAF, and reset the EFI fuse. That should help

LOL....you posted while I was looking for the tire size calculator.....

Where did you get the ethanol free gas???


Tire size calculator

 

[4-Ripcord]

LOL....you posted while I was looking for the tire size calculator.....

Where did you get the ethanol free gas???


Tire size calculator

Phillips 66 in Taos.

 

[PitbullRescuer]

You guys that are getting these great MPG #'s, what years are your trucks? Just curious if the electronically controlled throttle vs. the cable operated throttle impacts the MPG's.

 

[madbomber08]

I have a 5 spd with 265 70s and recently I've seen anywhere from 18 - 19, but it's been abnormally warm this winter. That's mostly town miles as well, not so much stop and go driving but I still considerate town driving.

 

[ALBPM]

2002...

When I went from 265/75s to 285/75 E weight tires last May my gas mileage dropped from around 17-18 to 15-16 for mixed city and highway driving.

I cleaned my MAF and Throttle Body installed a Borla muffler and an Injen intake using the new dry Amsoil filter. My mileage went back up to 17-19 MPG for my weekly use.

I drove from Albuquerque to Edgewood a couple weekends ago ~35 mile trip one way. At 70-75 MPH got 21 MPG going out and 23 MPG coming back per my Scangauge II.

 

[98OzarksRunner]

I recently put on some Cooper A/T3 load range C tires and my mileage went up a little more than 1 MPG (but then came down a little when I added the weight of an ARB bumper and Warn winch). I'd check the air in the tires. I'm running my tires at 40 PSI (I think, maybe 45) where the older standard load range tires ran at 32 PSI. If they don't have enough air that will kill mileage.

 

[Running4life]

I just drove over 1K miles from TX to Alabama and back-averaged 17mpg. When I had the 265/70/16 tires I was getting 19 or better. It seems no matter how I drive 17mpg is the average.

 

[jrm]

If youre coming from a

P rated 265/70/16 to a LT rated D or E load range tire your mileage will decrease due to the difference in rolling weight between the two tires. Also are the tires aired up to the specs labeled on the sidewall?

Another thing i notice on long trips is the climate, particularly wind factors will also affect my mileage. Lastly anything over 70mph kills my mileage.

 

[Hepar]

I was getting roughly 18/19 city and 24/25 freeway before my 265/75-16's. Now I get around 14/15 city and maybe 18 freeway.