Chevrolet Volt Gets 230 MPG City Fuel Economy Rating

By Chris Haak

08.11.2009

Earlier this morning, GM finally revealed what the “230” viral marketing campaign has been all about for the past few weeks.  As many suspected, the number represents the fuel economy of the upcoming range-extended electric Chevrolet Volt – specifically, the city fuel economy.  The highway figure will be significantly lower, but still better than nearly every car on the road.

The figure is based on a new methodology developed by the EPA specifically for plug-in electric vehicles that assumes more [electric] city driving than the standard EPA fuel-economy tests.  From GM’s press release:

Under the new methodology being developed, EPA weights plug-in electric vehicles as traveling more city miles than highway miles on only electricity. The EPA methodology uses kilowatt hours per 100 miles traveled to define the electrical efficiency of plug-ins. Applying EPA’s methodology, GM expects the Volt to consume as little as 25 kilowatt hours per 100 miles in city driving. At the U.S. average cost of electricity (approximately 11 cents per kWh), a typical Volt driver would pay about $2.75 for electricity to travel 100 miles, or less than 3 cents per mile.

GM had been lobbying the EPA to devise a special test for plug-in range-extended EVs that “give them credit” (my words, not GM’s) for the fact that some 70% of daily commutes are less than 40 miles roundtrip, so the Volt theoretically could use nearly zero gasoline during normal driving, so a little number crunching/playing on the EPA’s part is not surprising.

The 230 miles per gallon number certainly is eye-popping.  While details of the test procedures were not released for public scrutiny, gm-volt.com reported that Mike Duoba, a scientist at Argonne National Laboratory, was able to nearly duplicate the 230 mpg number in his tests:

Mike Duoba from Argonne National Lab devised a method to determine the MPG of an EREV; first the car is driven from a full battery until it reaches charge-sustaining mode, then one more cycle is driven. If we use the highway schedule, the first 40 miles are electric.  One more cycle is 11 more miles. If the Volt gets 50 MPG in charge sustaining mode, it will use .22 gallons of gas for that 11 miles.  Thus 51 miles/.22 gallons = 231.8 MPG.

Unsurprisingly, the more miles driven between the Volt’s overnight charges, the poorer the fuel economy number will be.  Driving the car across the country won’t get anywhere near 230 miles per gallon, but driving it across town might actually get an infinite mileage number because no gasoline would be used.

The 2010 Toyota Prius is the current mileage champ (at least among mass-production cars available in the US), and it’s rated at 48 mpg city/51 mpg highway.  Depending on the distance of the EPA highway cycle test for the Volt, its highway rating is likely to be closer to the Prius’ 51 mpg number (it has a similarly aerodynamic shape and will have a 1.4 liter engine vs. the Prius’ 1.8 liter, but may weigh more with GM’s traditional hefty engineering and additional battery capacity).

This number is certain to get GM some positive attention when the company is desperately trying to spruce up its environmental image in the eyes of the public (and likely its government owners).  The idea of driving a car and rarely needing to refuel it, not to mention paying a fraction of the price of gasoline for electricity (the Prius at 50 mpg costs about 20 cents per mile for gasoline assuming $2.50 per gallon, while the Volt is quoted at less than 3 cents per mile).

Of course, Toyota is not sitting idly by and allowing GM to steal its spotlight.  A plug-in Prius is coming in a few years, and GM has the pesky problem of selling buyers on its $40,000 230-mpg car when Toyota is offering a $23,000 50-mpg car.  Tax incentives will help GM bring the price difference down to about $10,000, but still, $10,000 buys a lot of miles’ worth of gasoline at 50 miles per gallon and $2.50 per gallon (200,000 miles).

I have a suspicion that these are just the opening salvos in the new decade’s fuel-economy wars.  The horsepower war is, sadly, winding down.

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