I disabled AFM as an experiment.

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by stchman, Aug 26, 2013.

  1. stchman

    stchman Active Member 2 Years 1000 Posts


    As of pulling into work this morning, I am getting a 18.6 average fuel economy. That's actually slightly better than previous tankfuls. So far so good.

    I did make a discovery, if I set the cruise at 65 I get a steady state(flat ground) reading from the instant economy gauge of 20-21MPG, if I set the cruise at 60, I get steady state of 23-24MPG. I hate going that slow, but the fuel economy is better. I'll just keep the cruise at 65 as going 60 is too painful.
  2. ChevyBoy2009

    ChevyBoy2009 Rockstar 4 Years 500 Posts

    My Diablo should be almost here and then ill see what my truck gets with it off
  3. bazar01

    bazar01 Rockstar 100 Posts

    I know how it feels to go 60 on a 65. I have been doing this for a while now but everybody is just passing me and giving me a strange look just to get 20 mpg on the average on a full size truck. :grrrrrr:
  4. stchman

    stchman Active Member 2 Years 1000 Posts

    Today is Friday.

    Average fuel economy for the 5 days of mostly highway, and a little city is 18.8MPG. I used less than 1/2 tank this week. This is of course only a small sample size, but it does look promising.

    I compromised and set the cruise at 63. I will keep the other forum members updated.

    Is the disabling of AFM a sure fire way to not have the oil consumption problem, or is there a possibility of the problem as the engine has the AFM hardware?
  5. Cowpie

    Cowpie Rockstar 3 Years 500 Posts

    Sure is a lot of anecdotal evidence that turning off the AFM has a beneficial effect on engine oil consumption. I know I will find out, probably more accurately than others, whether it makes a difference or a problem that is inherent to the engine design. I turned off the AFM the day my new 2013 came home from the dealer after buying it. If it has any AFM time, it was during the 9 miles from the dealer to my house. Other than that, it has no time at all in V4. So, over time, we will see if the oil issue crops up anyway. Also, since I got it, it only got the initial fill and one after that with E10. The rest of the time it has only gotten E85. Will see how that affects things over time also.
  6. stchman

    stchman Active Member 2 Years 1000 Posts

    I gather you bought a tuner when you knew you were going to buy that truck?

    Also, E85 only? I gather you can get E85 cheap. Unless you get E85 at at least $1 a gallon less, it is not worth it.

    E85 = crappy mileage.
  7. Cowpie

    Cowpie Rockstar 3 Years 500 Posts

    Well, it played out somewhat close. I bought the pickup, and it would not be ready for 3 days. While at home, I started surfing around and came across the AFM issue. After reading a considerable amount about it, including finding out about the Range AFM disabling device, I ordered it up. So, when the pickup got brought home, it got the new module put on it shortly after it got there. So it wasn't quite that I bought the Range module when I knew I was going to buy the truck, it was more like I bought the Range module Because I bought the truck. Else knowing about this issue before hand, It might have been the tipping point to persuade me to not buy the truck. Only the deals that were offered gave this pickup and edge, along with the reputation of the dealer I was using. I am not a huge fan of anything being produced, regardless of label on the grill, so I just look at what vehicle will do what I need done, has the most amount of features for the dollar, and do it at the best value I can get in my area.

    Now on the E85 issue. Yep, agree the mpg difference does make a difference. I am getting E85 at $2.39 a gallon. E10 is 3.36 a gallon and regular is 3.46 a gallon. Even with the mpg difference, I am saving roughly 3-4 cents a mile operating cost using the E85. I run multi layered relational spreadsheets tracking this kind of stuff in my commercial trucking operation, it is a short step to doing it for my pickup. And E85 does not equal crappy mileage. Using it in an engine that is designed for multifuels makes for crappy mileage. In an engine that is designed to ONLY run on a high level of ethanol, E85 or straight ethanol actually turns in some rather respectable mpg numbers. But since that wasn't an option, the point is moot.
    Last edited: Aug 30, 2013
  8. stchman

    stchman Active Member 2 Years 1000 Posts

    Range AFM, so that device needs to stay plugged into the OBD-II port all the time? My Hypertech handheld programmer simply re-programs the ECU

    If I could get E85 for $2.39 a gallon I would run it as well.

    According to fueleconomy.gov Silverados like our users have reported 17MPG combined with E10 and 13MPG combined with E85.

    In order to make E85 more desirable to use from a financial standpoint, E85 would have to be $2.57 a gallon. These are of course using your E10 and E85 prices you quoted.

    The problem is, most service stations here in my area E85 is either the same price or $0.15 lower. Not worth it at all.
  9. ChevyBoy2009

    ChevyBoy2009 Rockstar 4 Years 500 Posts

    Diablo showed up 30 mins ago!...will give updates after i drive it
  10. JJK1

    JJK1 New Member

    Exhaust gas is retained and compressed over and over againin the deactivated cylinders – This can’t be good for the engine – I would think it may be the cause of the need for new rings in these motors. This never happens if the engine stays in V8 mode. The exhaust gas is never prevented from being ejected in v8 mode.

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