Richard Truett
Richard Truett
Technology and Engineering Reporter

Look who's leading the small-car mileage race

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Here’s an interesting little irony from Ford’s embarrassing restatement of its fuel ratings for six vehicles: The new, low-price Mitsubishi Mirage just pulled ahead of the Ford Fiesta SFE and is now the most fuel-efficient gasoline-powered small car in America.

This is low tech vs. high tech, and low tech is winning.

EPA fuel-economy figures revised after Thursday’s restatement show the Fiesta SFE with its 1.0-liter three-cylinder EcoBoost engine is now rated at 31 mpg city, 43 highway and 36 combined. The manual transmission Mirage has an EPA rating of 37 city, 44, highway, and 40 combined.

The Mirage’s 1.2-liter three-cylinder engine doesn’t have any of the whiz-bang technology of the Fiesta SFE. There’s no direct fuel injection, turbocharging, external balancing, variable oil and water pumps, or split cooling system to be found in the Mirage.

Open the Mirage’s hood and you see a basic, no-frills car engine – well-engineered, efficient and capable of delivering its EPA ratings or better.

Granted, the Fiesta is a premium small car with many features not available in the Mirage. And the horsepower and torque ratings of the two cars don’t compare. The Mirage’s engine generates just 74 hp, while the Fiesta SFE’s engine cranks out a respectable 123 hp. But there’s an asterisk here.

The Mirage weighs a lot less than the Fiesta, 1,973 pounds vs. 2,537 pounds for the lightest models of each. So that power deficit in real-world driving is not as bad as it looks on paper.

As long as Ford is coming clean about its fuel-economy figures, a little more honesty about EcoBoost engines seems appropriate.

Ford’s EcoBoost engines are great motors. But they are not fuel-economy engines as Ford ads would have consumers believe. They are high performance engines that offer the potential for great fuel economy.

But Ford drivers rarely realize that potential.

Why? Because the turbocharger is a guilty pleasure, like chocolate or reality TV. Once the smooth rush of power from the turbo comes on, you become hooked and your fuel economy declines. By blasting a more dense mixture of fuel and air into each cylinder, the turbocharger makes a tiny engine act big. We Americans like our acceleration.

There’s only one way to extract fuel-economy numbers from an EcoBoost engine that are close to EPA ratings: drive the car with the lightest feet, which bypasses the turbocharger. And when you do that in a vehicle such as the Fiesta, it performs very much like a Mirage, and isn’t a lot of fun to drive.

On the EPA’s fueleconomy.gov Web site, drivers can self report their own fuel economy. I couldn’t find one EcoBoost-powered vehicle where drivers reported attaining the window label number or better. There are even more self-reported fuel economy figures on Fuelly.com, and again owners of EcoBoost vehicles are reporting lower fuel economy than the EPA window label on the “Average MPG” rating, which is roughly equal to the EPA’s combined figure.

The few Mitsubishi Mirage drivers who self-reported show a greater number meeting or beating the EPA combined rating. On Fuelly.com, 17 Mirage drivers have reported their fuel economy. Eight beat the 44 combined rating, one tied it and 8 came up short.

I’m not sure if champagne corks are popping at Mitsubishi, which is battling back from a decade-long slump. The company sure could use some good news. But spokesman Alex Fedorak says the Japanese automaker is studying the fuel-economy situation and might just promote the Mirage as America’s most fuel efficient gasoline –powered small car.

“I don’t know what kind of Mirage advertisements are coming, but if you are the leader, you want the world to know,” Fedorak said.

It wasn’t that long ago that Ford boasted about beating Toyota in fuel economy “in every segment the two companies compete.”

With the lightweight aluminum F-150 coming soon, all eyes will be focused on the pickup’s fuel economy. The target set by the Chrysler’s Ram EcoDiesel is high -- 28 mpg highway. It will be interesting to see if Ford will be as aggressive with its F-150 mpg claims now that it has been burned twice.

You can reach Richard Truett at rtruett@crain.com.

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