MT vs AT fuel economy

[redthies]

Probably beating a dead alpaca here, but does anyone have any actual real figures on how AT treads compare with MT treads in the same size? Tire makers would have us believe there is a difference, but if I drive on a 35" MT in my 12valve Cummins, and then do the same drive with an AT, will there be a significant difference??

Thanks for any info!

 

[chasespeed]

From MY experience, my diesels seem to do a little better on the hwy with M/Ts.....and by a little better, I do mean just that....

The gassers I have owned, M/Ts hurt the mileage.

 

[Hilldweller]

Really depends on the tires, tread compound, weight, rolling resistance, inflation pressures, aerodynamics, etc.
My numbers have gone both ways with different brands and models.

 

[Deleted member 9101]

When I switched from BFG A/T to Firestone Destination M/T's on a 1996 F-150 I lost about one to two mpg...but it looked cool and thats all that mattered...lol

 

[AxeAngel]

My mpg went down dramatically when switched from 29" A/Ts to 33" M/Ts

-Sam

 

[AFSOC]

Not a close comparison to your rig but I will throw it out there anyway. A couple of years ago on my XJ I replaced 235/75-15s BFG AT with 9.50x30-15 BFG MT. I lost 1.0 MPG using the slightly larger BFG MTs with 3.55-1 ratio diffs. The comparitive test was each direction on a trip from Pennsacola to Tampa. Same route, same speed, no elevation change. It was as close to a controlled test situation as I could have engineered if this circumstance hadn't presented itself.

 

[strider3700]

I had bald to the point of being slicks m55's changed then to a mild AT and lost 1 mpg but had a huge gain in traction.

 

[CA-RJ]

There are many factors to weigh. Many manufacturers have different weights and diameters for different tread designes of the same size. For example--

285/75R16
BFG AT--
Weight 59 lbs
OD 32.8"

BFG MT KM2
Weight 59 lbs
OD 33.1"

Even that .3" of an inch is more roating mass and is slightly bigger which will give you less mileage overall.

 

[SpencerFitch]

There are many factors to weigh. Many manufacturers have different weights and diameters for different tread designes of the same size. For example--

285/75R16
BFG AT--
Weight 59 lbs
OD 32.8"

BFG MT KM2
Weight 59 lbs
OD 33.1"

Even that .3" of an inch is more roating mass and is slightly bigger which will give you less mileage overall.

But they weight the same.

Not to mention bigger tires get you more miles than you spedometer reads.

Such as.. switching from 30" to 33" you may loose 2 MPG at the pump but you have to factor in the 10% increase difference in the miles you actually went. So if you had 18mpg before and droped to 16mpg plus 10% = 17.6 which means you only lost .4MPG

 

[strider3700]

By going larger yes the reported miles would be lower then they actually are bit at the same time the rpm necessary to maintain any given speed in any gear would have dropped and that may result in fuel savings.

In order to have any chance at a reasonable comparison between MT and AT which I think the original poster wanted we would have to stay the same size.