5.7 hemi milage

Discussion in 'Heavy Duty' started by hextall, Jan 8, 2017.

  1. billa9b0ng

    billa9b0ng Member

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    2014 Ram 2500 SLT CCSB
    Engine:
    Hemi 5.7
    I drive 67 - 70 on the highway and do a bit better. Your mileage sounds about right for driving that speed.
     
  2. NewBlackDak

    NewBlackDak Senior Member

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    I lose 1 mpg for every 5 mph over 65. It's a big brick, and it takes a lot of energy to push it through the air.


    Sent from my iPhone using Tapatalk
     
  3. hextall

    hextall Junior Member

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    Thanks much for the replies. I was incorrect in the rpm. It's closer to 2000. I did get a little better coming home from my trip over the weekend but still only about 11.5. Again this seems normal so I'll just deal with it. Just was concerned something was wrong but it seems ok. Thanks all. Hoping I can enjoy this truck.
     
  4. tnt2671

    tnt2671 Member

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    thats about exactly what i average 11.3 to 12
     
  5. HS-LD

    HS-LD Member

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    Location:
    NE Oregon
    Ram Year:
    2017 2500 Tradesman
    Engine:
    6.4L Hemi
    What I've learned about HD MPG's so far:

    62mph is the magic speed.

    A Magnaflo muffler will get you +1-2 mpgs. K&N filter maybe something, CAI maybe +1.

    Drive like grandma.

    MPG's is worse the first 10,000 miles. It seems to get better at 500 and then at 3-4000, and then at 8-10,000. (I always wondered if the computer has a break in protocol?)

    Bigger tires or a leveling kit or hauling stuff makes it go down.

    No wind, 10,000+ miles, freeway with cruise at 62mph, unloaded, no traffic, flat land, 89 oct good gas, should get 16+ mpg.
     
  6. 68PowerWagon

    68PowerWagon Senior Member

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    Yea my 6.4 took a major nose dive when the winter blend came out. Went from about 16-17mpg to 9-10mpg.
     
  7. NewBlackDak

    NewBlackDak Senior Member

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    Mine does too. Make lots of sense. We want to reduce emissions, so we'll make them burn 30% more fuel.


    Sent from my iPhone using Tapatalk
     
  8. zogg

    zogg Senior Member

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    Location:
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    Ram Year:
    2017 Ram 1500 Bighorn 4x4 quad cab
    Engine:
    Hemi 5.7
    I had a 2013 ram 2500 4x4 with the 5.7. Around town I got about 12-13 mpg, but on the hi way it was much better. With 25,000 miles on the truck we went from Illinois to Arizona unloaded and drove between 65 and 75 mph for the whole trip. We consistently got 18-19 mpg on 87 octane.

    We bought a new fifth wheel and traded for a 2016 6.4 4x4.....what a disappointment in mpg compared to the 5.7......if I get 15 hi way I'm surprised. Ugh.
     
  9. stembridge

    stembridge Member

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    Thank you, farm subsidies! I have a friend who farms about 2000 acres of corn and soybeans, and he'd like nothing better than to see the subsidies done away with. It impacts a *lot* more than the corn market - everything from fertilizers to beef prices get screwed up (not to mention the deleterious effect on our vehicles).

    es
     
  10. SouthTexan

    SouthTexan Senior Member

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    For gasoline, it is summer blend fuels that have additives to help the environment by lowering its RVP making it less volatile at higher temperatures, not winter. Summer fuel has about a 2% higher energy content due to these additives which is one of the many reasons why you get better fuel mileage in the summer. Winter fuel does not have these additives so it has a higher RVP which increases it's volatility so it can be easily burned in colder temperatures. You would have a lot harder time starting a vehicle with summer fuel on a very cold day than you would with winter fuel. It would also run rough.

    There are other things that decrease your mileage during the winter as well like lower tire pressure and the air being more dense. For every 10 F the outside air drops, your tire psi will drop about 1 psi. So if it was 35 psi at 100 F, then it is 25 psi at 0 F. Colder air is also more dense than warm air which means you have to apply more load on your engine in order to push through it. The research we did at Cummins showed a 2% increase in aerodynamic drag for every 10 F decrease in temp.

    Also, for gasoline engines, colder more dense air will cause the engine to burn more fuel to stay at the optimum 14.7:1 stoichiometric air/fuel ratio. Basically 14.7 air to 1 fuel. Gasoline engines have to stay around this ratio at all times in order to run correctly and not damage the engine. Since colder air is more dense, there is more of it in a given space. Therefore the engine reads this from the MAF sensor and adds more fuel to compensate for that increased air density. If it didn't add more fuel then it will run lean which damages gasoline engines.

    This is why intakes generally hurt fuel economy on newer gasoline engines since the MAF sensor will tell the ECM to add more fuel for any extra air added. This is not the case for diesels since they run lean just about all the time so intakes generally make them more efficient. Under load diesels run about 16:1 and at around 140:1 at idle.
     
    Last edited: Jan 12, 2017
    2015HD and Cmsharp like this.

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