Horrible Gas Mileage with KM2's

I just purchased some 285/75/16 BFG KM2's last week and have noticed a dramatic decrease in my MPG's. My trip to work in the morning consists of about 10 HWY miles and 3 miles on the street and I have noticed a decrease in this area.

I also took a 110 mile-trip to Big Bear this weekend which consisted of a 7,000 ft elevation gain. I had a full cab plus some minor luggage in the back which totaled to about 800-1,000 lbs. Total driving this weekend was about 280 miles which left me with 1/4 tank after it was all said and done. This comes out to ~14MPG!!!

I'm running my tires at 32psi. I know they are heavier than stock and my 2.5 inch lift plays a role in the decrease as well, but was wondering if you guys are experiencing similar symptoms?

 

I think im running mine at like 40 psi. I dont know my gas mileage but my light comes on at like 275 miles. It is worse than stock obviously. I have the same size tires as you.

 

wow. well if my calculations are right, I should be getting ~350 miles per tank, which is a bit better than yours so maybe I shouldnt be complaining. When putting the tires on I didnt expect such a noticeable difference in MPG.

 

350 til light comes on or all of it?

 

IM guessing all of it? I never let my light come on and the 350 MP tank assumption is based on the fact that I'm getting about ~90 miles per 1/4 tank.

 

Are you accounting for speedometer error?

 

I've checked my mileage 3 different times since I have had my truck and I just turned over 12K miles. I'm only getting 14.5 MPG and that was with stock 265/70/R16 BF Goodrich Rugged Trail tires. I'm now running the Goodyear Duratrac's 265/75/R16.....I'm probably getting worse MPG now.....to afraid to check.....I don't want to know!

 

I just figure i burn 15 gallons at the light. So if i take my 275/15 thats about 18mpg

 

I'm only getting 320 miles per tank on a stock setup, but with a pretty new truck

 

If your truck had 265/70/16s stock then putting 285/75/16s will make your speedometer and odometer read 7.31% too slow. To correctly calculate fuel economy, multiply your mileage by 1.0731, then divide by the number of gallons.

 

then im getting 19.6

 

I am also running 32 psi in all 4 of my tires but I am running 285/65-18"s with a 3" lift kit. I know I lost mpg for sure, I just never looked into it. I figure that's the price I am going to have to pay for wanting to modify my truck. So I just suck it up and live with it!!

 

x2.

 

If you calculated correctly, then yes.

There are alot of people who complain about how much their big tires have killed their gas mileage, but fail to take into account speedometer error.

 

Yeah thats very true. I know when it says 75 on my speedometer, the GPS reads like 78.9 or something like that.

 

That small difference adds up when calculating fuel efficiency,

 

Yeah understood. I dont know. Maybe one of these days I will calculate my mpg and see where I'm really at.

 

For me, it doesn't really matter. I didn't buy the Tacoma for good gas mileage, otherwise I would have bought a Prius. Its a truck for crying out loud!

 

X2 on that one!!!

 

Ask OakleyTRD about gas mileage.