WOBURN, Mass. -

Congratulations, California, home of the top three cities having high MPG, eco-friendly used cars. On the flip side, Detroit is, well, guzzling gas.  

These are just a couple of results as analysts at iSeeCars have released their comparison of the 20 largest U.S. cities by percentage of cars with the best and worst miles per gallon vehicles. 

The data, based on analysis of 25 million used cars listed on iSeeCars.com over the past year, lists the San Francisco area as having the most eco-friendly cars, at almost 10 percent, while the Los Angeles metro area has almost twice the number of fuel-efficient cars as New York City. 

The company defines best MPG cars as eco-friendly vehicle which get 30 miles per gallon or higher. Worst MPG rated vehicles are those getting 22.5 mpg or lower.

“The top three cities with the highest percentage of eco-friendly cars are all in California, perhaps not too surprising since the state has some of the best incentives for buying hybrid and electric cars,” said Phong Ly, chief executive officer of iSeeCars. 

Other highlights of the report:

—Collectively, about 6 percent of vehicles nationwide are eco-friendly, fuel efficient vehicles while 66 percent are gas guzzlers.

—The top 10 cities represent 32 percent of all best MPG vehicles nationwide while the largest 20 cities make up almost 50 percent.

—Chicago and New York City have about equal number of cars listed for sale, but Chicago has 30 percent more eco-friendly cars.

—California has 8 percent of the used cars listed for sale, but has 12 percent of all the eco-friendly and high MPG vehicles nationwide.

—Phoenix is on both top 10 lists for having the highest percentage of best and worst MPG cars.

—Of the largest 20 cities by population, the top three cities with the highest percentage of gas guzzlers are Detroit, Minneapolis and Denver.