Gas Mileage Difference Between These Two Engines?

I'm going to be upgrading from a Chevy Impala to a Chevy Silverado 2500 or GMC Sierra 2500, so I'll be experiencing quite the drop is Gas Mileage

There are two Silverados I'm looking at, a 6.0L Gasoline Model Crew Cab with a Leveling Kit, K&N Intake, MagnaFlow Exhaust, Electric Fan, and it's Chipped.

The other one is a GMC Sierra 2500 8.1L Gasoline Model, Crew Cab with a 6" Lift and AirBags for the rear suspension. No other mechanical upgrades.

Between the two, as an estimate, what would be the difference is Gas Mileage (city is my primary concern), is there a big Horsepower Difference? Being that these are both Gas and not Diesel, is it defeating the purpose of getting a smaller engine because it's working harder?

I would mainly be using for everyday driving and occasionally would haul a Four-Wheeler or trailer. So nothing rough, basically it comes down to if there is a dramatic difference in Gas Mileage?

Thanks in advanced! Any information is helpful.

Update:

By the way, the Silverado is an 05' and the GMC is an 03'.

4 Answers

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  • 6 years ago
    Favorite Answer

    Agree with Preston. Only go with the 8.1L if you NEED the power. You will be lucky to get 10MPG FREEWAY with one of those things.

    Those chips/K&N/junk all leads me to believe that truck has been abused anyway. Only dumb owners do that sort of stuff, honestly. And only dumb owners abuse their vehicles.

    Cracks me up when I see a car being driven very hard with a "for sale" sign in the window. I don't need someone elses problems!

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  • 6 years ago

    Go with the Chevy 6.0. You will get around 12 to 16 that's if u have a light foot.

    • DarkNet-Magic
      Lv 5
      6 years agoReport

      I use cruise a lot, so I stick with a steady speed most of the time, even around the city. Would you happen to know the difference? I was told 13-14 MPGs by the owner for the GMC, but that's probably highway.

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  • 6 years ago

    Both suck on fuel but the GMC would be better. By the way, the K&N's dont do crap

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  • JES
    Lv 6
    6 years ago

    Probably the two worst choices.

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