Green is still a red-hot buzzword in the auto industry, with carmakers competing to showcase their commitment to fuel savings. It’s not all altruistic; carmakers have to meet tougher fuel-economy standards between now and 2025. And not every winner is a paragon of green technology. But each vehicle we spotlight is the least thirsty in its class based on annual fuel cost.

The annual fuel cost assumes 15,000 miles of combined city and highway driving each year and fuel prices of $3.20 a gallon for regular, $3.40 for premium and $3.95 for diesel. Models must make our top 25 in their category to be eligible, and no model can win the award if another trim level of that model has won in a lower-price category.

Source: Data comes from TrueCar.com

14 Most Fuel Efficient Cars, 2012

Sticker price: $15,995

Invoice price: $15,231

TrueCar national average price: $15,978

3-year resale value: 53%, 5-year: 37%

City mpg: 36, Hwy: 37

Only ten feet long, the iQ is the world’s smallest four-seater. But don’t let the size fool you. Scion packed the micro-subcompact with 11 airbags (including the industry’s first rear-window airbag), standard Bluetooth and HD radio technology. The 1.3-liter engine puts out 94 horsepower and gets 37 miles per gallon in combined city and highway driving.

Cars Under $20,000: Scion iQ

Sticker price: $24,760

Invoice price: $23,320

TrueCar national average price: $22,209

3-year resale value: NA, 5-year: NA

City mpg: 51, Hwy: 48

America’s favorite hybrid leads the midsize class in fuel economy with 50 mpg in combined city and highway driving. It was Kiplinger’s Best in Class winner last year, with the most cargo space in the midsize class and plenty of legroom for all passengers.

Cars $20,000-$25,000: Toyota Prius Two

Sticker price: $29,975

Invoice price: $29,349

TrueCar national average price: NA

3-year resale value: 47%, 5-year: 34%

City mpg: 126, Hwy: 99 (electric vehicle, mpg equivalent)

Mitsubishi’s electric iMiEV took first place in the Environmental Protection Agency’s Fuel Economy Leaders list this year, with a combined city and highway mpg equivalent of 112. The tiny EV offers zero tailpipe emissions for $6,000 less than the Nissan Leaf (and it’s eligible for a $7,500 federal tax credit), but you’ll trade price for interior space.

Cars $25,000-$30,000: Mitsubishi iMiEV ES

Sticker price: $36,050

Invoice price: $34,557

TrueCar national average price: $36,191

3-year resale value: 47%, 5-year: 36%

City mpg: 106, Hwy: 92 (electric vehicle, mpg equivalent)

The first mass-market electric vehicle to hit the streets, the Leaf boasts serious amenities in addition to a “fueling” cost of less than $700 a year. Heated seats and mirrors are standard features for 2012, as is a seven-inch information display with navigation, Bluetooth and a USB connection for music. The price tag is steep, but it’s tempered by a $7,500 federal tax credit.

Cars $30,000-$40,000: Nissan Leaf SV

Sticker price: $42,575

Invoice price: $39,657

TrueCar national average price: $41,211

3-year resale value: 55%, 5-year: 39%

City mpg: 25, Hwy: 33

The winner of Best New Car in its class this year, the A6 packs a powerful yet thrifty turbocharged 2.0-liter engine. Its roomy interior is comfortable and elegantly styled, befitting the brand’s reputation for quality interiors and fit and finish. Plus, German-engineered handling comes baked in.

Cars $40,000-$50,000: Audi A6 2.0T Premium

Sticker price: $54,595

Invoice price: $50,601

TrueCar national average price: $51,239

3-year resale value: 54%, 5-year: 37%

City mpg: 27, Hwy: 32

Striking the perfect note between power, efficiency and luxury isn’t easy, but Infiniti manages it with the hybrid variant of the M35. Far less costly than its luxe hybrid competition (all over $90,000), it puts out 360 horses and gets 29 mpg in combined city and highway driving.

Cars $50,000 and Over: Infiniti M35h

Sticker price: $49,545

Invoice price: $45,655

TrueCar national average price: NA

3-year resale value: 56%, 5-year: 38%

City mpg: 22, Hwy: 34

BMW’s drop-top racer gets a new inline 4-cylinder engine for 2012 as well as notably thrifty fuel economy. Direct-injection technology and turbocharging help it produce 240 horsepower (more than the inline 6-cylinder it replaces).

Sports Cars: BMW Z4 sDrive28i

Sticker price: $31,395

Invoice price: $29,234

TrueCar national average price: $30,088

3-year resale value: 51%, 5-year: 35%

City mpg: 34, Hwy: 31

One of the best-selling models in the U.S., the Ford Escape Hybrid offers the best fuel economy (32 mpg combined) and the only hybrid powertrain in the compact crossover segment. But 2012 is your last chance to get it -- the Escape undergoes a major redesign for 2013 that will drop the hybrid variant.

Small Crossovers: Ford Escape Hybrid

Sticker price: $46,110

Invoice price: $42,039

TrueCar national average price: $44,965

3-year resale value: 60%, 5-year: 44%

City mpg: 32, Hwy: 28

The Lexus RX crossover offers both luxe and green cred with the RX 450h hybrid. Its high resale value, spacious interior and high mpg -- it gets 30 in combined city and highway driving -- earned it Kiplinger’s Best in Class nod, too.

Midsize and Large Crossovers: Lexus RX 450h

Sticker price: $74,800

Invoice price: $70,000

TrueCar national average price: $73,380

3-year resale value: 50%, 5-year: 34%

City mpg: 20, Hwy: 23

Hands down the green vehicle with the most bling, Caddy’s big SUV hybrid has combined city/highway mileage of 21 mpg (a considerable improvement from the gas-engine’s 16 mpg combined). Escalade’s green credentials come at a high price, though: nearly 75 grand.

Truck-based SUVs: Cadillac Escalade Hybrid (TIE)

Sticker price: $52,615

Invoice price: $49,773

TrueCar national average price: $50,831

3-year resale value: 46%, 5-year: 32%

City mpg: 20, Hwy: 23

Chevrolet’s hybrid Tahoe shares many of the same underpinnings as the Escalade, and it ties with the Cadillac for Most Fuel-Efficient -- but offers a sticker price that’s $22,000 less. Despite its size, it has reasonable service costs and respectable fuel economy (combined mileage of 21 mpg).

Truck-based SUVs (TIE): Chevrolet Tahoe Hybrid

Sticker price: $53,115

Invoice price: $50,246

TrueCar national average price: $51,627

3-year resale value: 55%, 5-year: 39%

City mpg: 20, Hwy: 23

GMC’s Yukon hybrid is more or less the twin of the Chevy Tahoe, but it boasts significantly higher resale values without a huge difference in price. Annual fuel cost is $2,259 ($530 less than the gas-engine model).

Truck-based SUVs (TIE): GMC Yukon Hybrid

Sticker price: $29,035

Invoice price: $26,390

TrueCar national average price: $27,498

3-year resale value: 55%, 5-year: 41%

City mpg: 18, Hwy: 27

Winner of Best in Class for the second year running, the Odyssey’s thrifty 3.5-liter V6 gets 21 mpg in combined city and highway driving, and annual fuel costs are just $2,267. The Touring model adds a 6-speed automatic transmission that boosts mileage by one mile per gallon in the city and on the highway.

Minivans: Honda Odyssey LX

Sticker price: $27,160

Invoice price: $25,337

TrueCar national average price: $26,732

3-year resale value: 62%, 5-year: 48%

City mpg: 44, Hwy: 40

The newest addition to the Prius family nearly swept Kiplinger’s wagon awards this year -- winning Best New Wagon and Best Resale in addition to Most Fuel-Efficient. It has the cargo capacity of a small SUV but gets 42 mpg in combined city and highway driving.

Wagons: Toyota Prius v Two

SLIDE SHOW: Best Resale Value Cars

SLIDE SHOW: Best in Class Car Values

SLIDE SHOW: Best Values in New Car Models

TOOL: Our 2012 Vehicle Rankings

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