Fastest fuel-efficient cars

With an eye toward a fast but fuel-efficient future, we've compiled a list of the quickest, most fuel-efficient cars on sale in the U.S.

Behind the Numbers

To compile our list, we evaluated combined city/highway gas mileage, horsepower and torque (the amount of force the engine delivers to the drive shaft). We awarded points on a place basis (one point to first, two points to second and so on) to the vehicles with the best fuel economy and highest horsepower and torque, with the scale weighted 2:1 toward speed. The 10 vehicles with the least points made our list. As a bonus, we're including two super fast all-electric cars.

Our tally includes the Spyker C8, a quarter-of-a-million dollar Dutch sports car that makes the 0-60 sprint in 4.5 seconds, topping out at 187 miles per hour (300 km/hr). For just under $200,000 US, the Aston Martin DB9, with a 0-60 time of 4.6 seconds and top speed of 190 mph (305 km/hr), comes in at No. 5. No. 1 on our list: the $130,000 Porsche 911 Turbo, whose 480 horsepower and 460 ft lbs of torque push it to a top speed of 193 mph (310 km/hr).

The essential duo of horsepower and torque is what makes these cars fast. While horsepower will keep a car revving at blindingly fast top speeds, it's the oft-unheralded torque that gets it there in the first place.

"When you think of a car, everybody thinks of horsepower, but what you feel when you press the pedal is actually torque," says David Paja, director of marketing for passenger vehicles at Honeywell, which makes turbochargers for BMW, Ford and Jaguar among others.

Green Speed Demons

Granted, "fuel efficiency" is a relative term, and the economy ratings of the vehicles on our list are less than stellar.

But speed and efficiency don't have to be mutually exclusive. Turbochargers and diesel technology both enhance power while squeezing out the most energy from every last drop of fuel. Both play important roles in how engineers develop increasingly efficient, quick cars.

Peter Schwarzenbauer, an Audi board member, says Audi has improved fleet-wide fuel efficiency by 30 per cent since 1995, due largely to integration of diesel engines like the one developed in the super-fast R15 TDI racecar (600 horsepower, 800 ft lb of torque and a top speed of 205 mph or 329 km/hr).

The $114,200 Audi R8, No. 9 on our list, has benefited from similar innovation. It uses direct injection in its 4.2L V8 engine to achieve a combined 15.5 mpg (15 litres/100km)and a 0-60 acceleration of 4.4 seconds.

Rob Moran, a spokesman for Mercedes-Benz, says engineers at the company's high-performance arm, AMG, focus on using differently tuned transmission modes and start-stop functions to make cars like the SLK55 AMG (No. 10 on our list) more efficient. Aluminum components and carbon fiber body panels also increase fuel efficiency because of their light weight.

Minute improvements like those may seem woefully incremental at best, but on a finely tuned supercar, every little bit helps.

 

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