With gasoline prices inching closer to $4 and even $5 a gallon, more Americans will make high gas mileage a priority when they buy their next car. The good news is that new technologies allow high levels of engine efficiencies that were previously unattainable. Some electric cars get well over 50 miles per gallon. Several hybrids get more than 40 MPG, as do several cars that run on very small four-cylinder engines.

Read America’s Most Fuel Efficient Cars

Automakers are manufacturing more fuel-efficient vehicles because the market for them has grown. These days, there are many more cost-conscious buyers, as well as people who want to use green cars. The first Toyota Prius hybrid was built in 1997 and went into global production barely a decade ago, in 2001. The first Chevy Volt all-electric car went on sale just a little more than a year ago, in late 2010.

But the increased production of high-mileage cars is not just because of the increased demand. The federal government also will require car companies to produce much more fuel-efficient vehicles in the future. President Obama’s new fuel economy standards call for car companies to have fleetwide average MPG of 54.5 by 2025. For that to happen, the number of hybrid and electric car models will have to grow rapidly.

24/7 Wall St. asked the U.S. Department of Energy for a list of the most fuel-efficient cars for sale in America. Each of the 10 most fuel-efficient cars were reviewed for MPG, engine type, configuration and the cost of fuel over the course of a year, as well as the cost of the vehicle.

Average MPG is based on a combination of city and highway driving. In the case of hybrids or electric cars with auxiliary gas engines, the average MPG of the two engine types in the vehicle were combined. Research firm Edmunds or the vehicle manufacturers themselves provided car prices. The annual cost of fuel is based on 45% highway, 55% city driving, 15,000 annual miles and current fuel prices. Those fuels price are, of course, rising by the day right now.

These are America’s most fuel-efficient cars.

8. 2012 Honda Insight
>MPG: 42
>Engine type: hybrid
>Car type: Front wheel drive, compact
>Fuel cost per year: $1,329
>Sticker price/base model: $18,350

Two Honda (NYSE: HMC) Insights made the list of fuel-efficient cars — the base Insight and the AV-S7 model. Unlike some of the other cars that get very high gas mileage, the Insight has full seating capacity for five people, which Honda’s smaller hybrid, the CR-Z, does not. The base price of the Honda Insight is well below that of most of the cars on this list, which probably reflects Honda’s attempt to lure hybrid buyers away from the mass market. Honda has added a number of interactive features meant to “engage” the driver in the fuel-monitoring experience. This includes an “ECON Button” that modifies various vehicle systems to help minimize its overall energy use — and maximize fuel efficiency.

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7. 2012 Toyota Camry Hybrid LE
>MPG: 41
>Engine type: hybrid
>Car type: Front wheel drive, mid-sized
>Fuel cost per year: $1,361
>Sticker price/base model: $29,500

The Camry Hybrid is a good example of a car manufacturer adding a hybrid version to a well-known, established brand of gas-driven models. The Camry is Toyota’s base 4-door sedan that sells for $21,955. This base model gets average gas mileage of only 25 MPG in city driving and fuel costs up to $1,993 per year. The hybrid version costs $8,000 more than the base model, so consumers have to trade upfront costs against future savings on fuel costs over time. Toyota (NYSE: TM) has placed the Camry Hybrid just above the Prius in both size and price.

6. 2012 Lexus CT 200h
>MPG: 42
>Engine type: hybrid
>Car type: Front wheel drive, luxury compact
>Fuel cost per year: $1,329
>Sticker price/base model: $29,120

Toyota’s luxury nameplate, Lexus, is one of a growing number of luxury car lines that have begun to offer hybrids. The fuel efficiency trend has progressed enough that even some full-sized SUVs now come with hybrid engines. The full-sized flagship Lexus S comes in a hybrid version, selling for $129,750. The CT, a five door hatchback, is the brand’s entry level vehicle. It comes in a base and an “F” series sport model. The base price for the “F” is $37,995. The car goes from zero to 60 in 9.8 seconds. That qualifies as slow for a sports car, but not one that gets 42 MPG.

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5. 2012 Honda Civic Hybrid
>MPG: 44
>Engine type: hybrid
>Car type: Front wheel, four-door sedan
>Fuel cost per year: $1,268
>Sticker price/base model: $24,050

Honda took the highly successful Civic, already known for its fuel efficiency and quality ratings, and added a hybrid engine option to its lineup. The Civic now comes in seven models that range from a $15,805 sedan to the high-end “Si” coupe. Honda will push further into the alternative engine space with a new Civic Natural Gas model. This model has a base price of $26,155. Satellite links and luxury packages can push the price of the Civic Hybrid well over $27,000. Honda has begun to offer attractive financing packages to quicken Civic Hybrid sales. This includes a 0.9% financing option over a period as long as 60 months. This could mean that Honda either cannot sell many of the cars, or that it is willing to invest to take market share from its rivals.

4. 2012 Toyota Prius
>MPG: 50
>Engine type: hybrid
>Car type: Front wheel drive mid-sized
>Fuel cost per year: $1,116
>Sticker price/base model: $23,015

The Toyota Prius has three models among the top 11 most fuel-efficient cars sold in America. The Prius now comes in a base model, a smaller “c” model designed for urban driving, and the Prius V four-door wagon. The Prius is the undisputed king of the alternative energy car market. The car went through three generations of development since it was first sold in Japan in 1997. Toyota also produced an all-electric version last year, when Prius sales passed the three-million mark worldwide. The Prius and the Honda Fit hybrid exchange the spot as the top-selling car per month in Japan. For the entire year 2011, Prius took the top spot with 252,528 units sold.

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3. 2012 Azure Dynamics Transit Connect Electric Van
>MPG-equivalent: 62
>Engine type: Electric
>Car type: Front wheel drive van
>Fuel cost per year: $972
>Sticker price/base model: $22,035

Unlike the other vehicles on this list, the Azure Transit Connect is a commercial truck. It was launched by Ford (NYSE: F) and Canadian car component company Azure in mid-2010. It comes in both a basic and wagon size. The initial sales goal for the light truck were extremely modest. Reuters reports that sales are expected to be less than 2,000 this year. Like most commercial vans, the Transit Connect has a full rear door, two floor-to-ceiling side doors, and a wheel base longer than most passenger cars.

2. 2012 Nissan Leaf
>MPG-equivalent: 99
>Engine type: Electric
>Car type: Front wheel drive, mid-sized
>Fuel cost per year: $612
>Sticker price/base model: $35,200 (editor’s note: does not include tax credit)

The Leaf was a major model launch for Nissan and its partner Renault. Reuters reported at the time the Leaf was first released that “Nissan and Renault are counting on an aggressive push into the nascent electric car market to boost their brand image — much as the Prius hybrid did for Toyota Motor Corp.” The Leaf was originally available in only seven states — Arizona, California, Hawaii, Oregon, Tennessee, Texas and Washington. By July 2011, as more capacity came online, Nissan marketed the Leaf in a number of states. Unlike Mitsubishi, Nissan already has a large presence in the U.S. The company sold 79,313 cars and light trucks in January, up 10% from the same month in 2011. With a nearly 9% share of the American market, Nissan has the dealer network and marketing tools to push the Leaf as a major alternative engine car.

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1. 2012 Mitsubishi i-MiEV
>MPG-equivalent: 112
>Engine type: Electric
>Car type: Rear wheel drive subcompact
>Fuel cost per year: $540
>Sticker price/base model: $29,125

Mitsubishi is one of the least successful major car companies that offers a fleet of cars and light trucks in the U.S. During the month of January, Mitsubishi sold only 4,711 cars in the North America, down 18% from January of last year. The Japanese company has, however, decided to offer the i-MiEV early this year to compete with more well-known electric cars like the Chevy Volt and Nissan Leaf. The federal government is so anxious to drive the market for fuel-efficient cars that it offers a $7,500 tax credit for people who buy the car. The American Council for an Energy-Efficient Economy recently named it the Greenest Car — the first time an electric vehicle has taken the number one spot.

-Douglas A. McIntyre

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