I have been getting some really BAD BAD mpg. like 8-10 MPG. I did a search on here and found a few posts about head work and MPG being related. these posts were from early last year. what should i tell my dealer when i go in? i know they are going to say it is due to the 35's. but i know that is total BS. since i have nad the tires for some time and never had this issue..

any help would be great.

 

PS.. i just went out and had OnStar run a test. everything looked ok..

 

TonyH3, don't forget you need to add 10% to what ever you see on the odometer because of the 35's, but that is still low even with the 10 % added.

 

DUDE U DRIVE A HUMMER DONT BE A CHEAP A$$, you dont buy a car if you cant afford the gas.....


J/K
I would like to know also I have been having a bit of the same problem and the car seems to be running fine.

 

Tony,
My experience with larger tires is that they will kill your fuel mileage and HP. Before I bought my 08' H3 Alpha I drove a F350 Powerstroke Diesel that I had many performance mods on such as a TS Chip, High-flow air-intake, 5" exhaust, ATF Turbo and too many other things to mention. I ran around 350hp and 700 ft/torq. on the rollers. My point being, when I went from 33� tires to 35� tires I lost 40hp just like that and my fuel mileage sh*t the bed too! I didn't believe that the tires were making the difference sowhile still at the dyno shop I switched back to the 33's and immediately got the 40hp back. Go figure! Everyone argued that it wasn't the size of the tire but the fact that the 35's were mud tires and the 33's were AT tires. BTW, they were 35" Toyo Mud's I had on thePowerstroke and I loved them!

So take it for what it's worth. All I know is the larger tires hurt my fuel mileage and HP.

 

i knew i would loose some HP and MPG. but the MPG loss is WAY WAY too much. also the fact that it went down in the last 2 tanks and not the 10 since i have had the tires on. something changed in the last 2 tanks..

 

Did you change the brand of Fuel in the last (2) Tanks? Did you reprogram the TCM to the new size tires. I notice this with allot of people who get new tires and up the size never mention about reprograming your vehicle pcm's which will reduce mpg severely because everything is thrown off. JMO

 

Not trying to hyjack this thread but how does one "reprogram the TCM" to help compensatate for the larger tires? I changed my tire size to 33" tires when the truck was brand new so I have no idea of what my real MPG should be.

 

no reprogram. just had the tires installed and drove.. get the same gas as usual..

 

tony I have gotten 9-10 mpg from day one....35's will effect your gas mileage by 3 mpg MAX...anyone that says it's more hasn't recalibrated the odometer and may think they are getting like 8 mpg less when really it's in the 2-3 range. Or they are going from tiny tires to a 35, not from 32's or even 33's like the adventure to a 35...one full size up will not effect it that much. I've been building lifted trucks my whole life and have dealt with this issue alot. You have an 06, does your vin fall in the range of the bad batch of heads? Mine does and that is what I feel the problem is, but the dealerships have no clue how to diagnose ANYTHING that doesn't come up on a dumb scan tool so.... I only got 11-12 mpg with the base 32's on the truck, so my mileage always sucked.