1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

99 MPG in V4 when stopping

Discussion in 'Performance' started by tkdgirl, Apr 29, 2021.

Sponsored By: Black Bear Performance
  1. tkdgirl

    tkdgirl TYF Newbie

    Posts:
    14
    Likes Received:
    10
    Joined:
    May 25, 2019
    Name:
    Rosalyn
    My 2011 XL Denali just started spitting crazy fuel MPG. Starts in V8 with regular mpg but when I slow down, it turns on V4 and the mpg goes way up when stopping. The only thing different recently is using E85 to top off my tank. This morning, it was really sluggish and hard to excel between 30-55. Tonight it was fine but still had the weird mpg stuff Anyy ideas? Range AFM device will be here Saturday, thankfully.

    20210429_203750.jpg
     
  2. gooffeyguy

    gooffeyguy Full Access Member

    Posts:
    2,771
    Likes Received:
    3,944
    Joined:
    Apr 11, 2018
    Location:
    St. Louis
    Name:
    Tom
    Just wait till you go down hill!

    Lol

    Sent from my SM-G930V using Tapatalk
     
    FrankU and tkdgirl like this.
  3. Sparksalot

    Sparksalot Full Access Member

    Posts:
    1,188
    Likes Received:
    2,215
    Joined:
    Sep 20, 2020
    Location:
    Texas
    Name:
    Rex
    With the Range device, you'll be able to see 99mpg in V8 mode.
     
  4. tkdgirl

    tkdgirl TYF Newbie

    Posts:
    14
    Likes Received:
    10
    Joined:
    May 25, 2019
    Name:
    Rosalyn
    Why does it do this though?
     
  5. Jason in DLH

    Jason in DLH Cheeseburger and Fries

    Posts:
    1,365
    Likes Received:
    1,468
    Joined:
    Sep 4, 2020
    Location:
    MN
    Name:
    Jason
    Because you get the best miles per gallon coasting (especially down hills as @gooffeyguy mentioned).
     
    tkdgirl likes this.
  6. BG1988

    BG1988 Full Access Member

    Posts:
    2,123
    Likes Received:
    875
    Joined:
    Nov 14, 2018
    Name:
    Brent
    normal

    It's called Deceleration fuel cut off (or DFCO)
    it will take a bit for it to adjust to E85, E85 is about 105 octane..


    mine will be here Friday or Saturday also :D
     
    Last edited: Apr 30, 2021
    Bill 1960 likes this.
  7. swathdiver

    swathdiver Full Access Member

    Posts:
    12,728
    Likes Received:
    13,530
    Joined:
    May 18, 2017
    Location:
    Treasure Coast, Florida
    Name:
    James
    Perfectly normal for a stock tune.

    How often have you been topping off with E85 and what exactly does that mean? Also, are you pumping 87 or 91/93 octane gasoline?
     
  8. tkdgirl

    tkdgirl TYF Newbie

    Posts:
    14
    Likes Received:
    10
    Joined:
    May 25, 2019
    Name:
    Rosalyn
    This was the first time since I was in an area that had E85. Not a lot around here. Otherwise it's 91+ per the manual.
     
  9. swathdiver

    swathdiver Full Access Member

    Posts:
    12,728
    Likes Received:
    13,530
    Joined:
    May 18, 2017
    Location:
    Treasure Coast, Florida
    Name:
    James
    The engines love E85, as it is basically like a race gas. You won't get the full benefits of power until you've run 3-4 consecutive tanks of it. Running it occasionally does help keep the system clean. If you run a mix you might get slightly better gas mileage and reduce your fuel bill. Mine, not a 6.2 Denali, gets its best mileage mixing 5-6 gallons of E85 and 20-21 gallons of gasoline.

    If you don't already use it or something similar, download the Gas Buddy app to your phone to see where E85 and E15 is sold in your travels.

    What's your favorite part of owning the Yukon XL Denali?
     
    tkdgirl likes this.
  10. tkdgirl

    tkdgirl TYF Newbie

    Posts:
    14
    Likes Received:
    10
    Joined:
    May 25, 2019
    Name:
    Rosalyn
    So far, my favorite part is the power this 6.2L puts out. Drives like a dream. Looks pretty but is all business. Looking forward to towing to see how well it does. Really happy with it so far.
     
    avalonandl likes this.

Share This Page