A new study from Consumer Reports says many new vehicles with small turbocharged engines fail to deliver the mileage advertised by automakers.
"We were surprised," said Jake Fisher, director of automotive testing for Consumer Reports. "We expected much better fuel efficiency from these engines."
The Consumer Reports tests raise serious questions about the performance and popularity of vehicles with turbocharged engines.
With the national average for a gallon of gas increasing 18 cents in the last week to hit $3.52 per gallon, car and truck buyers are likely to look at turbo chargers as a way to get better mileage than comparable models with standard, naturally aspirated engines.
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Several automakers with models tested by Consumer Reports refute the findings of the study.
Lower Mileage Than Promised
When Consumer Reports tested eleven vehicles with turbocharged engines, the organization found all eleven delivered fewer miles per gallon than the Environmental Protection Agency (EPA) fuel economy estimates for each vehicle.
Model [EPA MPG] [CR MPG]
Dodge Dart 1.4L Turbo 4  
Chevrolet Cruze 1.4L Turbo 4  
Ford Fusion 1.6L Turbo 4  
Ford Fusion 2.0L Turbo 4  
Hyundai Sonata 2.0 Turbo 4  
Kia Optima 2.0L Turbo 4  
Ford Escape 1.6L Turbo 4  
Ford Escape 2.0L Turbo 4  
BMW X3 2.0L Turbo 4  
Kia Sportage 2.0L Turbo 4  
Ford F-150 3.5 V6 Turbo  
Standing by Turbochargers
After seeing the results of the Consumer Reports tests, several automakers disputed the findings.
A spokesperson for Chrysler told CNBC: "Engines, turbocharged or naturally aspirated, have pros and cons and these are dependent upon specific usage, driving patterns and environmental conditions. The EPA test cycle is meant to provide a comparison on a consistent cycle. It cannot provide accurate numbers for every customer, every usage, and every environment."
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Wes Sherwood with the Ford Motor said, "In general, the Consumer Reports findings are not consistent with what we see from internal and external feedback on our EcoBoost engines. We're seeing people get the performance and fuel economy they want."
Ford's Big Bet on Turbochargers
Since the middle of 2009 Ford has been aggressively marketing its EcoBoost engines which feature a turbocharger and promise greater fuel efficiency. The company has sold more than a half million models with EcoBoost engines.
"Our customers are very happy with their EcoBoost vehicles," said Sherwood. Many of those customers paid between $700 and $900 dollars extra to buy a model with an EcoBoost engine.
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Consumer Reports says that may not be money well spent for those seeking better mileage.
"People should think before paying extra money for one of these engines," said Consumer Reports' Fisher.
Consumer Reports testing of turbocharged vehicles is different to the testing methods automakers use in conjunction with the EPA to arrive at MPG estimates.
Consumer Reports tests vehicles by physically measuring fuel economy with a precision fuel meter. The organization believes these are real world tests delivering an accurate reading.
When automakers test their vehicles and submit their results to the EPA for approval, they will use different "cycles".
Despite the differences in the tests, Consumer Reports stands by its findings.
"Our tests show that in many cases these turbocharged engines are not delivering better mileage," said Fisher.