Testing Turbos for Fuel Economy: Did Consumer Reports Compare Apples to Oranges?

Consumer Reports (CR) is one of the most trusted names in the world when it comes to independent evaluation of claims by product manufacturers. So when the magazine’s website published a report in February with a headline asserting “Small turbo engines don’t deliver on fuel economy claims,”  the article received a great deal of attention.

News organizations across the country, including the Associated Press, Jalopnik, the LA Times, Motor Trend, Reuters, the Wall Street Journal and hundreds of others, picked up the story.

Not so fast, says Stani Bohac, an associate research scientist at the University of Michigan School of Engineering, who specializes in engine systems. The CR story leads with a comparison of a turbocharged Ford Fusion against non-turbo models of Toyota, Nissan, Honda and other mid-sized sedans. But that mixes together a slew of variables which might impact fuel economy, says Bohac, without actually isolating the effect of turbocharging.

Research Scientist Stani Bohac, pictured in the University of Michigan Lay Automotive Lab, where he works to improve the fuel economy of internal combustion engines.

Research Scientist Stani Bohac, pictured in the University of Michigan Lay Automotive Lab, where he studies the fuel economy of internal combustion engines.

“I think their article is a little misleading and it’s not completely accurate,” he says. “It doesn’t say anything that’s not true, but their comparisons are not fair. They’re comparing apples and oranges to make an exciting story.”

“They compare a 1.6 liter-engine Ford Fusion with a turbocharger to competitor cars,” Bohac explains. “Toyota, Honda and Nissan make more fuel-efficient cars in that class with larger engines. Are the vehicle weights the same? Are the vehicle aerodynamics the same? Do they use the same gear transmissions with the same ratios?”

CR stands by its story: Eric Evarts, an associate automotive editor at CR, wrote the magazine’s piece on turbos. “From an engineering standpoint, it would be better to be able to compare Mcintosh apples to Mcintosh apples,” he told DrivingGrowth.org. “But I think given the consumer choice, it’s a better comparison. The consumer can’t choose something that an automaker doesn’t build.”

The Ford Fusion, he notes, is not available with a six cylinder engine, which powers the Camry, Accord and Altima. “If Ford is claiming they’re using a two-liter turbo in a high-trim Fusion to replace a V6 that’s thirstier,” says Evarts, “then I think consumers have a need to know that cars with that bigger V6 engine have better acceleration and also get significantly better fuel economy.”

CR buys its own vehicles and tests them on a track to simulate city driving and on an actual highway, says Evarts. It’s a different method than used by the U.S. Environmental Protection Agency, which tests vehicles on a dynamometer in laboratory conditions. CR’s fuel economy results are similar to EPA for conventional gas vehicles, says Evarts, but show less impressive MPG figures for hybrids, diesels ‚Äì and for downsized turbocharged engines.

CR’s test, on a single vehicle with four different drivers, recorded the turbocharged Fusion at 25 mpg. Non-turbo mid-sized sedans did better: 27 mpg for the Toyota Camry; 30 mpg for the Honda Accord; and 31 mpg for the Nissan Altima. (All vehicles scored lower in CR tests than in EPA ratings, but the drop was larger for turbo models.)

Turbochargers‚ which cycle air from engine exhaust through a compressor, to deliver more motive power‚ are supposed to allow smaller engines to perform like larger ones. Since smaller engines use less fuel, installing downsized turbocharged engines is one of the approaches being used by auto manufacturers and suppliers to meet new federal fuel economy standards.

In real-world driving conditions, Evarts suggests, drivers may accelerate more frequently to get a power boost from smaller, turbocharged engines, leading to a drop in fuel economy. If turbochargers don’t deliver as promised, manufacturers might have to go back the drawing board.

Ford is planning just the opposite, says company spokesman Wes Sherwood. “We’re bullish on it,” he says. The company recently announced a $200 million investment to build turbocharged EcoBoost engines at a facility in Cleveland. “We’re planning on having it across 90 percent of the Ford vehicle line,” says Sherwood. The company’s internal surveys, he says, show the EcoBoost “proving to be popular engines for customer satisfaction, and that includes for fuel economy.”

Raymond Williams works on a turbocharged Ecoboost engine at  Ford's Cleveland Engine Plant.

Raymond Williams works on a turbocharged Ecoboost engine at
Ford’s Cleveland Engine Plant.

Head to head comparisons, a mixed bag: CR tested 21 vehicles for its comparison of fuel economy in conventional gas engines vs. turbocharged versions. Six of the twenty-one were the same make and model with different engines, allowing for the head-to-head comparison suggested by UM’s Bohac.

Vehicle Consumer Reports MPG Turbo MPG % gain(loss)
Kia Optima
2.4 L Four 27
2.0 L Turbo Four 26 (-4%)
Kia Sportage  
2.4 L Four 22
2.0L turbo Four 21 (-4.5%)
Chevy Cruze
1.8L Four 26
1.4L Turbo 4 26 0
Ford F-150  
5.0L V8 15
3.5 V6 Turbo 15 0
BMW X3  
3.0 L six 22
2.0L Turbo 4 23 +4.5%
Dodge Dart  
2.0 L Four 27
1.4L Turbo 4 29 +7.4%

Source: Consumer Reports

The results were a mixed bag ‚Äì a bit different than suggested by the article’s categorical “turbo engines don’t deliver” headline. Two vehicles‚ the KIA Sportage and KIA Optima actually had worse fuel economy in a turbocharged version. Two ‚Äì the Chevy Cruze and the Ford F150‚ showed no improvement.

BMW’s X3, however, showed a 1 mpg gain in the turbo version, a 4.5% improvement. The Dodge Dart did even better, climbing from 29 mpg with a conventional engine to 31 mpg in the turbocharged version ‚Äì a 7.4% gain.

Bohac is currently testing how turbocharging and other equipment can be used to boost fuel economy and reduce emissions at the Lay Automotive Laboratory in Ann Arbor. He says the technology has been proven over decades of use in heavy duty trucks, which haul large loads over long distances.

“They have been using turbo for a long time,” he says. “It really works. They’re able to get more work out of a given size engine, as much as twice the power, and the engine is more efficient because of it. We’re starting to seriously think about that for passenger cars.”

A typical vehicle, he points out, has more than 10,000 parts ‚Äì and he’s convinced that accurate tests require singling out the impact of one component or system at a time. “I run track and field,” he explains. “If you give me the best running shoes in the world, and line me up against a professional runner wearing combat boots, I would lose. But that doesn’t mean combat boots are better than running flats.”

Roger Kerson is a Michigan-based media consultant for labor unions and environmental organizations.


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