If you want to buy a used Toyota Prius, don't go shopping for one in Detroit.

The Motor City has the worst fuel economy among used cars, according to a new study by iSeeCars.com, as reported by WardsAuto.

The study found that 71.2 percent of used cars in metro Detroit get 22.5 mpg or less. Minneapolis-St. Paul was the runner-up, with 71.1 percent of its used cars at 22.5 mpg or less, and Denver was third, at 70.9 percent.

In contrast, San Francisco had the best used-car fuel economy: Fully 9.5 percent of secondhand vehicles in the city rated at 30 mpg or higher.

The runners-up were also California cities: 8.8 percent of used cars in Los Angeles get 30 mpg or higher, as do 7.9 percent of used cars in Sacramento.

2008 Toyota Prius

2008 Toyota Prius

iSeeCars.com CEO Phong Ly said California's impressive showing wasn't too surprising, given the state's many green-car incentives.

California has always been more enthusiastic about green cars than any other state. Back in August, Toyota said its sold six of every 10 hybrids in California, and Californians also buy more plug-in electric cars than any other state.

Governor Jerry Brown recently signed six bills aimed at encouraging the proliferation of green cars.

The legislation included funding for 100 hydrogen fueling stations, extending solo High-Occupancy Vehicle Lane access to low- and zero-emission vehicles until 2019, and funding programs that encourage the purchase of newer, cleaner vehicles.

Among these is a "Cash for Clunkers"-style program that incentivizes ditching the dirtiest cars for cleaner ones.

Colorado--home of the third-worst city on the used car fuel economy list--has a similar program, albeit completely funded by the state's new-car dealers.

Meanwhile, while they may be rare on used-car lots, we wonder if used Prius prices might be lower in the Motor City--where they're obviously not wanted?

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