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Summary:

The battle of the MPGs kicked into high gear this week with General Motors making the bold claim that its upcoming Chevy Volt, an extended-range electric vehicle, will get 230 MPG for city driving. Nissan countered with an announcement that its 2011 all-electric LEAF sedan will […]

The battle of the MPGs kicked into high gear this week with General Motors making the bold claim that its upcoming Chevy Volt, an extended-range electric vehicle, will get 230 MPG for city driving. Nissan countered with an announcement that its 2011 all-electric LEAF sedan will get some 367 MPG — oh, snap! This banter of course raises questions about the validity and relevance of measuring the efficiency of cars that run on electricity in terms of how far they can go on a gallon of gasoline. (Check out the Atlantic, Consumer Reports, EcoGeek and Edmunds’ Green Car Advisor for some thoughtful discussions.)

Fritz Henderson Makes Volt Announcement

While we’re at it, how did GM really come up with that triple-digit MPG, and how does the company’s calculations compare with ratings for cars like the LEAF, gen-3 Toyota Prius, Smart Fortwo, Tesla Roadster and the Fusion Hybrid from Ford, which said earlier this summer that it’s making fuel efficiency improvements a top priority in upcoming lineups? We’ve put together a chart comparing fuel economy claims and methodology for these vehicles to help put them in perspective.

The EPA’s fuel economy rating system has plenty of critics (especially after a little revised number crunching by the agency disqualified some vehicles from the cash for clunkers program), but it does have relative transparency and consistency going for it. So even though real-world mileage varies from EPA ratings, numbers from the agency give us a sense of relative fuel efficiency of different vehicles on the market. The EPA isn’t vouching for GM’s 230 MPG claim, since it has not finalized the new rating system for plug-in vehicles and it has not tested the Volt, as the NYT Wheels Blog notes (GM’s Frank Weber says the model is slated for testing early next year).

In contrast with GM’s formerly-mysterious “230″ ad campaign and focus solely on city driving, and Nissan’s unexplained 367 MPG estimate (in a talk at the Plug-in 2009 conference in Long Beach yesterday, Nissan’s Mark Perry said the company used methodology for “a zero emission kind of world”), we know that the EPA has two tests to simulate city and highway driving. In both city (a stop-and-go 30 minute test) and highway (a non-stop 10-mile test averaging 48 MPH) tests, MPG estimates are based on the amount of emissions generated during the simulation and then adjusted downward to reflect real-world conditions, such as aggressive driving or cold temperatures. For plug-in vehicles with zero tailpipe emissions, clearly this system is lacking.

If you have ideas for how the rating system should work (perhaps a total overhaul to measure and highlight gallons per mile?)  — or if you see ways to improve our chart below or would like to see other vehicles added, please let us know in the comments.

Vehicle Fuel Economy: City/Hwy/Combined How MPGs Were Calculated Estimated Costs
2011 Nissan LEAF (electric) 367 MPG equivalent/??/?? Unknown. EPA Rated? No. “Less than the cost of gasoline”
2011 GM Chevy Volt (extended-range electric) 230 MPG/??/”Over 100 MPG” GM says it used “tentative EPA methodology” for testing plug-in vehicles, a 51-mile urban driving cycle, and reportedly 40 miles of electricity and 11 miles on the gas engine. However the EPA says it has not published even a draft protocol for testing plug-in vehicles like the Volt. EPA Rated? No. GM claims $2.75 per 100 miles for city driving (Assuming: 25 kWh per 100 mi)
2009 Tesla Roadster (electric) 135 MPG equivalent/??/?? According to former Tesla Marketing VP Darryl Siry, the total energy used for a full charge of the Roadster’s battery is 62.3 kWh (assuming a 15 percent loss). That’s equivalent to 1.85 gallons of gas for the 244 miles that the Roadster can go on a full charge – 244 miles divided by 1.85 gallons gives us a little less than the equivalent of 135 MPG. EPA Rated? No. $2.81 per 100 miles for city driving (Assuming: 62.3kWh at $0.11/kWh = $6.85 per charge, which is supposed to deliver a range of 244 mi).
2010 Smart Fortwo (diesel) ??/??/69 MPG This model is slated for the European market, so has a rating from the EU’s New European Drive Cycle, or NEDC system, which combines city and highway drive cycle tests. It’s meant to reflect European driving patterns. EPA Rated? No. About $3.81 per 100 miles at U.S. diesel prices (currently averaging $2.63/gallon)
2010 Toyota Prius (hybrid) 51/48/50 MPG Standard EPA tests: 11 mile stop-and-go city cycle, 10 mile highway with average 48 MPH) EPA Rated? Yes. $5.28 per 100 miles (using EPA estimate of $1.32 per 25 mi, $2.65/gal gas); $795 for fuel annually (assuming $2.65/gal gas and using the EPA’s default 15,000 mi/year, 45 percent hwy, 55 percent city)
2010 Honda Insight (hybrid) 40/43/41 MPG Standard EPA tests: 11 mile stop-and-go city cycle, 10 mile highway with average 48 MPH). EPA Rated? Yes. $6.32 per 100 miles (using EPA estimate of $1.58 per 25 mi, $2.65 gal gas); $946 for fuel annually (assuming $2.65/gal gas, and using the EPA’s default 15,000 mi/year, 45 percent hwy, 55 percent city)
2010 Ford Fusion Hybrid 41/36/39 MPG Standard EPA tests: 11 mile stop-and-go city cycle, 10 mile highway with average 48 MPH). EPA Rated? Yes. $6.80 per 100 miles (using EPA estimate of $1.70 per 25 mi, $2.65/gal gas); $1,019 for fuel annually (assuming $2.65/gal gas and using the EPA’s default 15,000 mi/year, 45 percent hwy, 55 percent city)
2009 Smart Fortwo (premium gas) 33/41/36 MPG Standard EPA tests: 11 mile stop-and-go city cycle, 10 mile highway with average 48 MPH). EPA Rated? Yes. $8.08 per 100 miles (using EPA estimate of $2.02 per 25 mi, $2.91/gal premium gas); $1,213 for fuel annually (assuming $2.91/gal premium fuel and using the EPA’s default 15,000 mi/year, 45 percent hwy, 55 percent city);
  1. [...] miles-per-gallon from a car that runs on electricity, anyway? Earth2Tech offers a cheat sheet of mileage claims from new electric cars and hybrids. Meanwhile, cash-for-clunkers is such a good idea Russia plans [...]

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  2. Walter Thompson Thursday, August 13, 2009

    While we’re on the subject of unbelievable fuel economy claims; How about the CSX’s claim of being able to transport 1 ton of frieght 430 miles on 1 gallon of diesel fuel? Since diesel locomotives weigh about 100,000 pounds, I find CSX’s claim to be unlikely.

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    1. Re Walter Thompson,

      As a train gets larger, the air drag per ton of freight goes lower and lower. So rolling resistance is the main energy loss for the vehicle itself, not counting engine heat discharged. Since steel wheels benefit from about .001 for their rolling resistance factor compared with rubber wheels that have .01 rolling resistance factor, this 430 miles for a ton of freight per gallon sort of compares to 43 miles per gallon for a one ton car.

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    2. have you somehow forgotten the mile long load of coal cars 2 locomotives can pull?

      you might want to do a bit of math before you go and say something is absurd.

      csx spent 185million on fuel in the second Q, now go find their 2q freight tonnage and do the math.

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      1. cliff,

        Who are you talking to, me, Walter, or CSX?

        Whatever, CSX did the math. I heard the same ad that Walter is quoting. Is it wrong?

        The coal train I recently saw in Kansas City had 6 BNSF locomotives pulling it, not that that matters in the present discussion. It was just amazing. It certainly brings home the fact that coal is the base of our electricity system. I heard that KCPL uses two such train loads every day — Could this be true?

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  3. [...] the carmaker says the Volt can travel per gallon of gas, news greeted with a mix of exuberance and skepticism. Many reporters, analysts, and bloggers see symbolism in Chevy’s very announcement, namely, [...]

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  4. Corporate honesty has just gone out the window… It’s no wonder that GM went bankrupt and nobody trusts them… Doing a little math of my own, it looks like they did the 51 miles on around a quarter gallon of gas. That means the “real” MPG is around 40-50 MPG. Pretty good, but not even as good as the Prius.

    I’ve got a pickup truck that will get 17 MPG… However, if I tow it for 40 miles, and run it for 11, then I come up with about 80 MPG… That’s pretty much the same thing that GM is doing… Lying bastards!

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  5. [...] Karma, will get the equivalent of 67.2 miles per gallon sounds downright modest relative to the triple-digit estimates we’ve been hearing in recent weeks from General Motors (230 MPG for the extended-range electric Chevy Volt) and Nissan [...]

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  6. [...] In a world where corporate transparency is very blurred and traditional mpg estimates seem so far from the real world performance of vehicles, I believe that MP$ could prove a more accurate, honest and relevant statistic for [...]

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  7. I’m throwing an idea out there for a new way to do ratings as you suggested in your article. The basis is measuring how many miles a car does per $ spent on fuel. Its a method with limitations I know, but consider for a second the positives: Its simple, universal, easy for consumers to understand & its not subjective so there can be no gaming or influencing of the figures. Let me know what you think:

    http://www.plentyways.com/blog/2009/09/miles-per-dollar-a-new-metric-for-fuel-economy/

    Thanks,

    Brendan @ PlentyWays.com

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  8. [...] about General Motors and Nissan’s triple-digit MPG claims for upcoming plug-in vehicles. “Electricity per mile” will be the shorthand of choice for the fuel efficiency of [...]

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  9. [...] is also developing highly efficient 3-wheelers (the electric 2e and hybrid 2h, both said to get the equivalent of 300MPG), are tempting. But Miller emphasized Green Lite is developing a different beast, notably [...]

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  10. [...] Volt, Nissan LEAF or Tesla Roadster and experience miles per gallon in the triple digits — as advertised — you may be sorely disappointed. Measurements of a car’s efficiency in terms of how [...]

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