05 lly 4X4 duramax w/2100 miles 35's w/6" lift 4x4 crew cab getting 10.8-11 MPG. What is wrong or is this normal with such low miles and larger tires? I've even had speedometer adjusted for the bigger tires and used the calculator to convert my numbers as I thought the onboard comp was off. Can anyone with the same setup reply with what they are getting?
Any helpful input appreciated !!!
KABster

All I can say is its normal, I had an 87 with 42"swampers 10"suspension lift 3" body lift and when you start lifting that messes with the aerodynamics of the truck creating more wind drag under the truck and adding larger tires create more rolling resistance and lowers your gear ratio all this makes your truck work harder to get it to go down the road thus lowering fuel mileage,you can change your gearing to a higher ratio (ex 3:73 to a 4:11) to get your truck back to its power band and ecomony and will help some but you will still have wind drag from the truck being lifted.

It all depends on how you drive. I am getting 320-360 miles on a tank (23-25) gallons. I filled up today I put 24.8 gallons of fuel in and reset the odo it had 348 miles. I drive pretty hard most of the time so my numbers may not help you. I think you are ok. Get you a programmer tell you ole lady you need it to get better economy.

you can change your gearing to a higher ratio (ex 3:73 to a 4:11) to get your truck back to its power band and ecomony



I've seriously considered this option.


I am getting 320-360 miles on a tank (23-25) gallons. I filled up today I put 24.8 gallons of fuel in and reset the odo it had 348 miles. I drive pretty hard most of the time so my numbers may not help you.


That seems like great mileage for driving it hard, I'm talkin easy off the signs and slow to the brakes 10.8-11 MPG w/my Duramax. Am looking into the Attitude complete mod setup but am in no hurry to get it done although I am quite anxious. Guess I'll have to go be extra job/chore oriented towards the wifes list and start suckin up again. Will need to rebuild wife credits from my last trucks add ons/ mods.

Thanks for the input!!!

My 02 Crew Cab with the Duramax/Allison combo gets between 16-19 in town depending on how many cars I kill. I run a 6" RCD lift with 35x13.50x18 Pro-Comp X-terrains, and it has 43,000 miles on it.

Sounds about right to me.-:t I think I've seen a best of 16 and 15 is more usual on the highway but arround town 10 to 14 is the best I can do. I calculate manually because the DIC is rarely correct.

15-16 city...highway ?. Still damn good for a lifted truck. Just think what the mpg would be if it was a gasser....-:t ...really crappy.


Enjoy....just drive it :ro)

Well as far as the mileage of a gasser...I get a solid 10 in the city and 12.5-13 on the highway...hearing what all you guys are getting makes me feel good...especially with the price of diesel around here.

I used to run a 315-70-17 (34.5) and got on average 14.9 DIC which, when adjusted (using 1.135), came out to just around 17 mpg. Now I'm running true 35-12.5-20's and adjusted using 1.15 came out to 15.7 mpg. This is all at 73-74 mph, corrected, on the freeway. I think the decrease is due to increased rotational mass ie, tire weight, and tire height.

Just my .02

Well as far as the mileage of a gasser...I get a solid 10 in the city and 12.5-13 on the highway...hearing what all you guys are getting makes me feel good...especially with the price of diesel around here.

You getting that mileage with 35" tires? I know my big block could barely get those numbers and it only 33" rubber on it.

Well as far as the mileage of a gasser...I get a solid 10 in the city and 12.5-13 on the highway...hearing what all you guys are getting makes me feel good...especially with the price of diesel around here.

Don't feel too good, I get 15mpg highway with a CC/LB/4WD/3500SRW/32.5" tires...









Towing 6000lb at 75mph. :D

My DIC says 13.2 I have never hand calculated. I don't worry about the mileage--I enjoy the power too much. My passenger mirror points doen towards my tip so I can watch the smoke. I know why my mileage is down. I would think you are in the ball park for mileage 35" tires.

You NEED to hand calculate using posted mile markers to get it right:

Your stock speedo is off.
Tuners mess up the DIC mileage.
Big tires screw you up unless you adjust the PCM.

Here's the deal.

Drive your vehicle 10 miles using the mile markers. compare the 10 miles with what the vehicle said you drove. In my case with 35's on my dually, there is about a 15.3% variance.

If you have a GPS, you can save yourself this step as it is accurate immediately. (ex. if your GPS says you are driving 70 and your odo says you are driving 63, then use that as your variance).

Next fill up your truck to the rim and reset one of your trip meters. Drive the tank and then refill to the rim. Read your mileage on the trip meter, and add the percentage variance to the mileage (ex. 300 miles times 1.15 = 345 ACTUAL miles driven in my case) Take the corrected miles and divide by the number of gallons used and you will have an ACCURATE MPG for your truck with larger tires.

The DIC is a useful tool but not very accurate. Good for general info purposes only.

BTW, dont forget the variance when it comes to changing your oil etc.

IMHO, anyone who says they are getting big MPG numbers with BIG tires is smoking weed or full of poo poo. It aint gonna happen. You want high MPGs, give up the bling. You want Bling, you will give up the high MPGs. IMNSHO...

Bonus for having big tires:

When you trade in your truck, if the odo. says you have 100k on the rig, you actually have 115k on it but you don't get dinged for driving that extra 15k. That's a whole year for free, according to NADA pricing guides.

I think a big thing with our trucks is to cruise at or below 2000 rpm's. My truck is used mostly on freeways and country roads. By no means do I take off easy when leaving lights but I've found 73-74 mph gets much better mileage than 76-77 mph(over 2000rpm's) when cruising.

Just my .02
Rich.

I adjusted my speedo with my Predator and checking with GPS the speedo was off .5mph at 55mph, I'm really happy with that. Way more accurate than I even hoped it would be.

I average 19mpg, but I regeared to 4.56 to take off most of that added effort turning those large tires...

The engine is stock. and the mileage is hand calced!
No poo-poo!
No Weed!

Towing 6000lb at 75mph. :D


:ro) That's what I'm talking about. ):h