• Apr 20, 2010
Last week at the Society of Automotive Engineers World Congress in Detroit, we spoke with Dr. Pete Savagian of General Motors about what the Chevrolet Volt's fuel economy sticker would look like. Last summer former GM CEO Fritz Henderson made a big splash when he announced that the Volt was getting approximately 230 miles-per-gallon combined. However, that number was based on a draft proposal by the EPA for a testing methodology for plug-in vehicles.

That proposal has never been made public, although it was believed to include running through the 11-mile test cycle repeatedly until the battery was depleted and then going through the cycle once more. The fuel consumption was then calculated based on the fuel used and the total miles driven. The 230 mpg figure drew a lot of criticism as being unrealistic, and for many drivers it would be. For others who drive short distances and charge regularly, it could actually be a conservative figure.

With only six months to go until Volt production begins, The Wall Street Journal is reporting that the EPA still has not finalized the mileage calculation procedure for these vehicles. The results you get are highly dependent on the driving duty cycle and a panel discussion at the SAE Congress on the subject of ratings did little to clarify the subject. GM's Savagian is confident that the EPA will finalize a test and labeling procedure soon, however. And they'd better, because by law, all new cars are required to carry a MPG sticker.

[Source: The Wall Street Journal]


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  • 39 Comments
      • 4 Years Ago
      Better measure: cost in dollars per mile traveled.
      • 4 Years Ago
      Volt is tiny. I can't wait for the big electric SUVs to come when fusion power goes online with unlimited supply of electricity.
      • 4 Years Ago
      MPG is deceiving and needs to change. An improvement of 18 -> 20 MPG has a greater effect than the improvement of 50 -> 60 MPG on the actual amount of fuel consumed. Gallons per 100 miles would be a better measure.
        • 4 Years Ago
        I think a better measure would be cost per mile.
        • 4 Years Ago
        @rossmorrill - That would mean the sales sticker would have to be revised for every price fluctuation. A car delivered to the dealer in winter would have fuel costs $.50-.75 cents cheaper per unit if it was still sitting on lot in May. The same hold true for electrical energy units. So there would have to be disclaimers on stickers stating some arbitrary cost case (ex. - 10 cents per mile @ $2.50/gal; 3 cents per mile on $3.80 per kwH).

        And given our education system, I do not see consumers being able to factor their current costs w/o some help. They probably do not even know where the calculator app is.
      • 4 Years Ago
      what's the difference here? No matter what the sticker says, you're never, ever, ever, ever, ever going to get the same mpg in your car. it looks good on paper, that's about it.
        • 4 Years Ago
        Both of my vehicles manage to get pretty much exactly what the stickers say I should get(updated '08 figures that is, since both are pre-'08 models). I actually get a couple of mpg's more than the stickers say most times.

        I don't hypermile virtually at all either, just drive normal in the city and use cruise control on the highway.
        • 4 Years Ago
        but are you actually keeping track of your mpg, or are you trusting the readout on your dash?
      • 4 Years Ago
      haha that's a great picture...

      Fritz: "FFFFFFFFUUUUUUUU!!1"
        • 4 Years Ago
        GM, lies?

        Never...
      • 4 Years Ago
      The Car can only drive so many miles on a charge, so how about
      how much juice it takes to fully charge the battery/ Total mileage per charge = kW/Mile
      then just run a normal test, driving the car on a completely dead battery

      I love how there is never a mention of how much these cars will increase your electricity bill.
        • 4 Years Ago
        Because the increase in the electric bill is massively offset by the decrease in the fuel bill you pay at your local gas station.

        It's not an even trade, the electricity will cost you much, much less than the same amount of gasoline would to travel the same distance.

        For instance compare the annual electricity cost of the Tesla to the annual fuel cost of even the Prius.

        $482 at $0.10/kW-Hr
        $963 at $0.20/kW-Hr
        vs.
        $858 at $2.86/gal. from fueleconomy.gov

        The figures are even more wildly in favor of the Tesla against any other vehicle since the Prius is quite efficient.
        • 4 Years Ago
        If you are worried about cost per mile then you have to factor in the cost of the vehicle, on this, the Tesla looses pretty badly.
      • 4 Years Ago
      I can't find any info about the EV1's Monroney(perhaps because they were leased and not sold?) but here's one for the Tesla Roadster,

      http://www.nytimes.com/imagepages/2008/11/16/automobiles/16sticker-inline1.html
        • 4 Years Ago
        Reply error, disregard.
      • 4 Years Ago
      We need to develop a new yardstick, since "miles per gallon" isn't going to easily transfer to every technology. I mean, what kind of "MPG" is a Nissan Leaf going to get when it's being charged by wind or solar power? The car doesn't burn fossil fuel, and generating wind or solar power doesn't either.
      • 4 Years Ago
      To wait this long after changing the rules and thus not giving GM a goal to shoot when production is set to begin soon is just wrong IMO. It could make or break this vehicle. Its whole marketable existence is based on its MPG rating.
        • 4 Years Ago
        I agree. While GM may have made a bad move by announcing the MPG based on a DRAFT proposal by the EPA, the EPA needs to step up and clarify their system.

        Part of it might be to get rid of MPG and switch to GPM. That would better relect the mileage of these vehicles, who potentially get infinite MPG.
      • 4 Years Ago
      There should be two figures 1) Infinity 2) what it gets when the engine is running.

      Otherwise, it is a random, useless number.

      If you think that will confuse people, then they are going to be really disappointed when they find out it doesn't get 230mph (or whatever random, useless number they pick).
        • 4 Years Ago
        Well, not useless. Gives the marketing people something to stamp all the literature with..
      • 4 Years Ago
      Why don't they just charge it fully, fill the tank all the way, and then just drive it around the course until it stops and see how many miles it went? Distance traveled/gallons used = MPG... That's how I measure MPG in my car, when I care.
        • 4 Years Ago
        That would make too much sense.
        • 4 Years Ago
        because that wouldn't accurately represent the possible advantages of a range-extender like the Volt. With that method, you are essentially reducing the Volt to a standard hybrid. However the entire point of the Volt is to make it possible to drive for daily, city usage on electric only, without the disadvantages(range and charging limitations) of a full electric like the Leaf.

        What I think would make the most sense, assuming the MPG standard is retained, would be to split it three ways; instead of city/highway MPG, you have a daily/commute/shortdistance driving number (which would be extremely high), a long-distance (i.e. standard highway mpg, basically) number, and a combined average, based on normal usage patterns. Surely there are studies sufficient to come up with something useful.
        • 4 Years Ago
        Sounds like a great way to encourage automakers to fit smaller fuel tanks. If they only put in 0.5 gallon of fuel, then they go 100 miles on electric power and 20 miles on the half gallon, they've got 240 "MPG"!

        The truth is that efficiency of an electric drivetrain can never be accurately represented by any measure that includes the word "gallons". And there is no answer for how to rate these cars that will really represent their performance for all customers. Even performance for the "average" customer is meaningless, because people vary way too much in the way they use their cars.

        The only right answer is to recognize that a single number simply will not do. It will never be an apples to apples comparison. People are going to have to use a little intelligence and evaluate vehicles based on their own needs. Those that do not posses that level of intelligence or care enough to bother to learn will most likely pay for their ignorance. Assigning a single number to these vehicles will only serve to make people more comfortable in their ignorance and encourage more of them to not really evaluate their needs. The general public will be worse off for it.
        • 4 Years Ago
        Agreed. But I would add the speed factor so with full charge+full tank:
        (Distance traveled at 25 mph)/gallons used = city MPG
        (Distance traveled at 60 mph)/gallons used = highway MPG
        Not perfect, but understandable.
      • 4 Years Ago
      If I were buying this car, I would like to see miles per charge on electric only and MPG on a depleated battery. Just keet these 2 values seperate. Also, I do like the idea of GPM as a addtion instead of a replacing MPG.
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