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Originally Posted by Wes Tausend
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They probably lie about the range to some degree. My wifes Prius only does about 36 mpg in the city now that it is so cold that the engine runs nearly constantly. This is opposed to about 46 mpg in warmer weather. She acts severely disappointed because they suggested 60 mpg city in the ads. 
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The mileage testing testing that the EPA used to use was flawed and it especially overstated the mileage for hybirds. Not only that but it is against the law for a car maker to publish a mileage estimate different than the EPA one.
So when hybrid manufacturers got complaints that the gas mileage was not as good as the EPA estimates, they were not allowed to state a more realistic one to their customers.
Truth in advertising was against the law in this case per the US government.
This was all reported in Consumer Reports a couple of years ago.
The flaw in the EPA MPG estimates testing was that it was based on measuring chemical content of the exhaust during the test. Well guess what? When a hybrid is running electric, there are no chemicals coming out of the exhaust.
I think the EPA has updated there testing recently though.