BS from GM

You’ve heard the extraordinary numbers – 230 miles per gallon!!  This is the claim GM is making for its new Chevy Volt electric car.  Watch this video

If a voice in the back of your head is telling you this is too good to be true – listen to it.  This claim is one of the biggest whoppers in advertising history.  The folks making these claims are counting on the listeners to be complete innumerate fools.  And the news media seems to be playing along with total credulity.  You would think there would be some kind of government crack-down on GM’s fraudulent claims.  Oh, I forgot, the government is GM.

Here are some important facts about the Chevy Volt.  It will be powered by an electric motor which is run off a lithium-ion battery.  The battery will have an energy capacity of 16 kilowatt-hours and will propel the car for 40 miles.  That works out to 0.4 kilowatt-hours of energy per mile.  The battery will have to be replaced after about 150,000 mile.

When the battery’s charge runs down, a gasoline powered electric generator will kick in to recharge it.  Gasoline has an energy content of 1.3 x 10⁸ Joules of energy per gallon. One kilowatt-hour is 3.6 x 10⁶ Joules.  So one gallon of gasoline contains about 36 kilowatt-hours of energy per gallon (1.3 x 10⁸ J0ules / 3.6 x 10⁶ Joules/kilowatt-hour).

So, if you could manage to squeeze every single kilowatt-hour of energy out of one gallon of  gasoline and into your battery, then one gallon of gasoline would drive your Volt 90 miles (36 kilowatts / 0.4 kilowatts/mile).  But there are pesky complications – like the laws of physics – that insure not even 90 miles per gallon will be achieved.  Conversions are not 100% efficient.  If you read the fine print, you will see that the reality is that if you drive your Chevy Volt on gasoline it will get, at most 50 miles to the gallon. 

Fifty miles per gallon is still pretty good you might say.  But $40,000 is a lot to pay to be squeezed like a sardine.  Consider this: a 1987 Honda Civic Coupe HF got 57 miles to the gallon.  It cost about $7500 dollars (about $16,000 in 2009 dollars).  And, you didn’t have to spend $15,000 to replace the battery every 150,000 miles in the old Honda. 

I drove a 1988 Honda Civic Hatchback for over 250,000 miles, always tracked the mileage, and consistently got 47 miles to the gallon.  I comfortably took my family across the country multiple times. Man, I miss that car.  I am not impressed at all by the over-priced hybrids or electrics that we are seeing today. 

So how does GM justify the preposterous claim of 230 miles per gallon?  The way they figure it, for every gallon of gas that you put in the tank, you will re-charge the battery enough times by plugging it into the grid at home to power it for 180 miles.  So, 50 miles from a gallon of gas and 180 miles from multiple charges from the electric grid at home. Voila! 230 miles per gallon.  They could just as easily claimed 1000 miles per gallon by figuring that you would charge it off the grid for 950 miles worth of power for every gallon of gas you pumped into the tank.

I think GM has a problem.  Most people who are likely to spend $40,000 on a little car have been around long enough not to be innumerate fools.