The Prius hybrid was once again the leader, with its fuel economy of 51 miles per gallon in city driving and 48 mpg on the highway, according to the Environmental Protection Agency’s testing methodology. Other vehicles in the top 10 include the Ford Fusion hybrid and its Mercury Milan twin, the Civic and Insight hybrids from Honda, and the Nissan Altima.

The only non-hybrid at the top of the list was the tiny Smart For Two from Daimler, which clocked in at 33 mpg city/41 highway.

Electric cars, such as the Tesla Roadster, are not included in the survey. The EPA is still trying to figure out how to measure fuel economy and greenhouse gas emissions in electric cars and plug-in hybrids in a way that would provide meaningful comparisons with traditional gasoline- and diesel-powered cars.

Overall, the top 10 fuel-efficient cars among the 2010 models are as follows:

1. Toyota Prius Hybrid (51 mpg city, 48 mpg highway)

The most popular hybrid car on the road today, this sedan is roomy and comfortable, and average on performance.

2. Ford Fusion Hybrid/Mercury Milan Hybrid (41/36)

The new Fusion Hybrid is a practical, mid-size sedan with an upscale interior of high-quality materials and unique technology features. It’s favorable driving characteristics have been noted in reviews.

3. Honda Civic Hybrid (40/45)

The Civic has Honda’s sporty performance and handling, but is a bit lacking on acceleration. A very efficient car, but a bit small for families.

4. Honda Insight Hybrid (40/43)

A small, sporty sedan which offers fewer features than the Civic, and priced to be an economy hybrid. The Insight is smaller than the Civic but larger than the Fit.

5. Lexus HS250h Hybrid (35/34)

A small, economical, reliable luxury sedan with all the creature comforts, and a full suite of optional electronic gadgetry. Sometimes described as a ‘luxury Prius with a trunk’.

6. Nissan Altima Hybrid (35/33)

One of the largest hybrids because it’s a mid-size sedan, but rear seat room isn’t a strong point for tall passengers. However, with 198 horsepower, it is one of the quickest hybrids on the road.

7. Ford Escape FWD and Mazda Tribute 2WD / Mercury Mariner FWD hybrids (34/31)

Roomy but not oversized compact SUV hybrids. Acceleration is leisurely, with only 133 horsepower.

8. Smart for Two Cabriolet / Coupe (automatic) (33/41)

Small two-seater, efficient for around town driving but a bit sketchy for the highway, despite advanced safety features.

9.Toyota Camry Hybrid (33/34)

Refined, roomy, and practical. Conservative styling and performance.

10. Lexus RX450h Hybrid 2WD (32/28)

One of the fuel-thrifty trio (with the Honda Fit and Nissan Versa) of small Japanese economy cars that arrived about two years ago. Toyota’s smallest car, but room for four 6-footers. Has a small, hardworking four-cylinder engine.

Understanding the new EPA Fuel Economy Label

Beginning with 2008 models, all new cars and light trucks sold in the U.S. carry window stickers which display the vehicle fuel economy estimates as determined by new test methods.

For more information about the new methods, see EPA’s Final Rule.

The new, improved features of the label are listed below:

1. New Methods: The label shows the estimated city MPG at the top left, and highway MPG at the top right. The estimates on 2008 and later models are determined using new, more realistic methods. During the transition year, comparison shoppers should compare models that are built in the same model year, so compare 2007 models to 2007 models, etc.

2. Estimated Annual Fuel Costs: The center of the label provides estimated annual fuel costs based on a given number of miles and fuel price, also listed on the label. Use this information to estimate fuel costs for this vehicle, and to compare fuel costs across different models.

3. Expected City Range: Estimated city MPG range appears at the top left, under the main city MPG estimated number. Most drivers can expect to achieve city fuel economy within this range.

4. Expected Highway Range: Estimated highway MPG range appears at the top right, under the main highway MPG estimated number. Most drivers can expect to achieve highway fuel economy within this range.

5. Compare to Other Vehicles: The lower center of the label gives a combined city/highway estimate for that vehicle, and shows where that value falls on a bar scale that gives the highest and lowest fuel economy of all other vehicles in its class (e.g. SUVs, minivans, compact cars, etc). Use this information to compare the fuel economy of this vehicle to all others within its class.

6. Your actual mileage will vary: The label includes a reminder that there are many reasons why your actual fuel economy may vary from the estimates. See www.fueleconomy.gov for fuel-saving tips.

7. For more information: The label provides a Web address where you can find out more information. See the Fuel Economy Guide at dealers or online at www.fueleconomy.gov.