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actual mpg for cng Cavs?

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  • actual mpg for cng Cavs?

    What mpg do you actually get with your CNG Cavs? I see a listing of 20/25 gas and 18/25 cng on

    http://www.fueleconomy.gov/feg/noframes/16403.shtml

    but I was expecting better mileage for such a small car.

    Is there much difference in mileage bt the auto and manual transmission models?

    Thanks,

    Doug
    Atlanta

  • #2
    Re: actual mpg for cng Cavs?

    Depending on how you drive it, average fuel economy seems to be between 25 and 30 with the mileage improving with the 4-speed auto and then with the Eco-tec engine in the '03 and '04 models. There are no manual transmission CNG Cavaliers. I can usually do 150 miles on a 5 gallon fill on the highway, a little better with the Eco-tec cars. Unlike a dedicated CNG only Honda, these cars are bi-fuel and the engine isn't optimized for CNG--so mileage suffers a little. But with a bi-fuel, you can always use 100% of your CNG without worry, so there is a tradeoff .

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    • #3
      Re: actual mpg for cng Cavs?

      First off, it is difficult to get an accurate reading of your MPG on CNG. There are many factors that play a role - the main one being you most likely will not get a full tank when you fill up. Pressure and temperature are the contributing factors.

      Your best MPG is on highway driving (obivously). City driving (starts and stops) kills your MPG on CNG. I have driven a 2001 (CNG fumigation system) and a 2003 (CNG injection system). The CNG injection system is better all the way around. Below are my conclusions about MPG or MPGGE.

      2001 CNG
      The worst I've seen is about 15 MPGGE. This is all city driving in the dead of summer with the A/C on.
      The best I've seen is about 31 MPGGE. This is all highway driving at about 55 - 65 MPH. It seems that if you drive above 70 MPH than your MPGGE goes way down. You get the best MPGGE at 55 MPH.

      2003 CNG
      The worst I've seen is about 20 MPGGE. This is also all city driving.
      The best I've seen is about 35 MPGGE. Again, when you go above 75 MPH your MPGGE goes way down. It seems that the best MPGGE is when you are 65 MPH or below.
      Jared.
      Mountain Green, Utah
      2003 CNG Cavalier
      2003 CNG Silverado 2500HD

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      • #4
        Re: actual mpg for cng Cavs?

        Thanks for the mpg info. I attached a couple of engine pics of a 2002 Cav I am thinking of buying. Can you tell me if that's the fumigation or injection cng system and if it is the Eco Tek engine?

        Thanks,

        Doug
        Attached Files

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        • #5
          Re: actual mpg for cng Cavs?

          Doug,

          The 2002 Cavalier has the "fumigation" system with the non-Eco-Tech engine. It is the same as the '98 - '01. The '03 - '04 Cavaliers have the fuel injection system with the Eco-Tech engine.
          Jared.
          Mountain Green, Utah
          2003 CNG Cavalier
          2003 CNG Silverado 2500HD

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          • #6
            Re: actual mpg for cng Cavs?

            I've got a 2003 bi-fuel Cavalier (fuel injected Eco Tec 2.2 ltr engine) and think Jared's ranges are proper on the top end, but too harsh on the low end. No matter how much city driving I have and A/C use I have, I've never got below 24 or 25 mpg. Generally is around 28 mpg either on cng or petrol. My highway mpg has been 30 to 33 even at speeds up to 70, but I agree that best is around 65 mph and up to 35 mpg if you can draft behind a large vehicle - - like consistent driving trucker !!

            Personal CNG mpg record is 39 mpg highway between Denver and Colorado Springs after a fill-up at Clean Energy public pump at new Denver airport. Ran cng tank completely empty so 39 mpg is legitimate.

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            • #7
              Re: actual mpg for cng Cavs?

              A couple of weeks ago I drove an '03 Cavalier from Auburn, California to the Salt Lake airport without refueling. I filled up with gasoline and CNG in Auburn. The CNG lasted for just over 180 miles (almost to Lovelock, NV) and the gasoline low fuel indicator turned on just as I was pulling into the SLC Airport CNG station. Over 600 miles without a fillup.

              The best range I've gotten with a 2002 Cavalier is from Orem, UT to Albuquerque, NM. Just under 600 miles. I was delivering the car to Tulsa and I didn't want to look around for a CNG station in Tulsa so I pulled the CNG fuse after about 100 miles of driving on CNG. I put the fuse back in when I got to Tulsa so I could show the buyer that the car was running on CNG.

              Another consideration of the Eco-tek engine vs the fumigation engine is the ability to handle changes in elevation. The fuel-injected engine adapts flawlessly to rapid changes in elevation. The fumigated system needs to be turned off and restarted so that the CNG computer can recalibrate to the higher altitude. Kind of frustrating when you're going skiing and there's not a convenient place to pull off and restart the car when it starts running poorly.
              2004 Toyota Avalon bi-fuel
              2013 Tesla Model S 85

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              • #8
                Re: actual mpg for cng Cavs?

                Contrary to above, mileage is easy to check on these cars. They all switch from CNG to Gasoline at the same point (250 psi if memory serves) giving a consistent end point to check. Fill the tank, reset the trip odometer & note the GGE purchased. Run the vehicle until it switches from CNG to gasoline and note the mileage, then do the math. Simple.

                Mine gets 32-33 mpg on CNG with about 30 % city, 70% highway driving. If strictly highway, it will get 35 mpg or slightly better as long as I stay under 75. It's an '04 model Cavalier.

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                • #9
                  Re: actual mpg for cng Cavs?

                  So if I'm averaging only 22-25 mpg in mixed driving in my '04 cav what should I be looking at? It runs great otherwise.

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                  • #10
                    Re: actual mpg for cng Cavs?

                    Originally posted by Ben Lurkin View Post
                    Contrary to above, mileage is easy to check on these cars. They all switch from CNG to Gasoline at the same point (250 psi if memory serves) giving a consistent end point to check. Fill the tank, reset the trip odometer & note the GGE purchased. Run the vehicle until it switches from CNG to gasoline and note the mileage, then do the math. Simple.
                    You may know the end point PSI, but it's not compensated for temperature and you never know exactly how full the tank is. And I've never found commercial pumps to give believable GGE numbers.

                    I don't think there's anything wrong with your Cav. Low to mid 20s is the normal mileage range.
                    02 GX
                    01 GX
                    03 Crown Vic
                    06 GX
                    Home Fueler

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