Results 1 to 2 of 2

Thread: Tire Size Effect on MPG

  1. #1
    Join Date
    Nov 2003
    Location
    Davenport Florida
    Posts
    268

    Default Tire Size Effect on MPG

    I am wanting to get the best MPG out of my new to me 2007 2500 CC LBZ with 248k on the clock. I drive MOSTLY unloaded, in Florida, and im only seeing 16 -17 mpg. The tires on the truck are very new 285/75/16 , and I do correct for larger tire size in mileage calculations, and use GPS to compare. Im wondering how much the larger tires effect the fuel mileage, and what difference I would see if I went back to the 245/75/16 size that came on the truck. From what I have found, my tires are 2" taller, so it raises the truck 1 inch. I have always heard lower truck = better mileage, but I dont know how much 1 inch will change things. Any experience / suggestions would be greatly appreciated.
    I am also planning to install a DSP5 and EFI tunes at some point. I want the economy tune, and the ability to switch to more power when I need it. I think this would give the best results for better mileage, over messing with the tires.
    email rfkjr@juno.com
    07 2500HD C/C LBZ 248k
    83 K2500 X 6.2, now 390 Stroker,18.5 & 19.5x 44 TSL\'s & Boggers,5.13w/Det.Lkrs. Mud Toy
    90 ISUZU, 350 eng, 350 trans, Double xfer cases, 2.5 Military Axles, Tractor tires

  2. #2
    Join Date
    Dec 2000
    Location
    Hawaii/Arizona
    Posts
    259

    Default

    Scooby,
    I would recommend using a Kennedy ECM tune. I have several tunes (Predator Diablo
    sport & Edge Evolution) that I do not like because of high EGT issues under load. The Kennedy tune gives a nice boost in HP and fuel mileage (25 MPG highway under 65 MPH) with relatively low EGTs. Additionally, I would stay with the 285/75/16 tires or smaller. I know someone that put a lift kit and 35" tires on his Duramax and now when he hits a hill (even a small hill) pulling his 40' toy hauler the truck goes into limp mode because the gear ratio is way off and it forces slipping in the transmission. My truck is a dually and the factory tires were 215/85/16. I converted it to 225/70/19.5 and had Kennedy do a 5% speedometer adjustment to the ECM when he installed his tune. The 19.5 tires have worked out very well on my truck but I would not recommend going to any larger tires on a dually. Good luck with your truck mods.
    John
    Last edited by CoyleJR; 03-24-2017 at 13:11.
    *2006 Chevy, 3500, 4X4, DRW, (LBZ) D/A, CC, LT, 252K Miles, 19.5" Wheels, Mag Hytec Transmission Pan and Differential Cover, SS Grill Guard, Racor 2 micron aux fuel filter, 100 Gallon Aux Fuel Tank, using Edge Evolution, Predator Diablosport, Kennedy ECM tune, Fitch Fuel Catalyst.

    *2006 Four Winds, Dutchman, 36', RV, D/A, 5500 Kodiak.
    *1993 Harley Davidson, Turbo charged, Springer Softail.
    *2007 Pontiac Solstice.
    *2005 Jeep, Liberty, CRD (diesel).
    *Full-timing in USA, see America first.

    BUY AMERICAN or CANADIAN, NOTHING from CHINA .

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •