In particular, the magazine singled out turbocharged versions of the Chevrolet Cruze and Ford Fusion, which it says don't boast the real-world performance or fuel economy figures their makers have suggested. Instead, Consumer Reports seems to be indicating that the engines have been tweaked specifically to perform well in the EPA-mandated fuel economy tests.
The Cruze comes standard with a naturally-aspirated 1.8-liter four-cylinder, but higher-volume LT and LTZ trim levels include an upgrade to a more powerful - and higher EPA-rated - 1.4-liter turbocharged four. Base Fusions, meanwhile, feature a naturally-aspirated 2.5-liter, but most trim levels are offered instead with either a 1.6 or 2.0-liter turbocharged four. The 1.6-liter Fusion is the model's EPA and sales volume leader.
"While these engines may look better on paper with impressive EPA numbers, in reality they are often slower and less fuel efficient than larger four and six-cylinder engines," Consumer Reports automotive testing director Jake Fisher said in a statement released to members of the media.
Those findings come in stark contrast to what some automakers have long espoused about turbocharging.
In its testing, Consumer Reports said that the Fusion 1.6-liter boasted the slowest 0-60 mph performance (8.9 seconds) among naturally aspirated rivals - the Kia Optima (8.6), Hyundai Sonata (8.4), Honda Accord (8.2), Nissan Altima (8.2) and Toyota Camry (7.7).
Similarly, the Fusion's as-tested combined fuel economy trailed the pack at 25 mpg. Leading the way were the 30 mpg Toyota Camry and Honda Accord and the 31 mpg Nissan Altima.
The larger Fusion 2.0-liter fared even worse. Its 0-60 mph sprint took a leisurely 7.4 seconds, a second behind V6-powered Nissan Altima, Toyota Camry and Honda Accord rivals. But the 22 mpg as-tested Fusion didn't counter with better fuel economy. The Altima (24 mpg), Camry (26 mpg) and Accord (26 mpg) all bested it.
By contrast, the turbocharged Kia Optima and Hyundai Sonata performed more in line with V6 rivals by hitting 60 mph in 6.6 seconds and achieving 24 and 25 mpg, respectively.
In the compact car arena, Consumer Reports discovered that while the Cruze turbo hit 60 mph 0.7 seconds faster than the naturally aspirated model, it achieved the same 26 mpg.
Conversely, the magazine's testing was more in favor of the Dodge Dart 1.4-liter turbo, which shaved 2.4 seconds off of the 2.0's 0-60 sprint and achieved 29 versus 27 mpg.
Consumer Reports also glanced at trucks and crossovers. It found slightly better performance and fuel economy for the 2013 BMW X3 2.0-liter turbo compared to the similarly-powerful 2012 BMW X3 3.0-liter naturally-aspirated. However, the magazine noted a mere 0.2 second improvement in the Ford F-150 3.7-liter V6 turbo's 0-60 sprint and no change in fuel economy compared to the F-150 5.0-liter V8.
The Los Angeles Times put together a convenient chart illustrating Consumer Reports' findings.
The magazine did not say whether it accounted for vehicle weight during its testing. The Fusion's base curb weight is slightly heavier than the rivals tested, although that difference could be nearly negated depending on equipment and trim levels.
While most Japanese automakers have stuck to refining existing technologies, some automakers have garnered big headlines by downsizing and turbocharging engines in order to, theoretically, keep power levels while reducing fuel consumption. In particular, Ford has stated that it plans for the vast majority of its new vehicles sold globally to be equipped with smaller, turbocharged engines over the next few years.
Hyundai and Kia have also aggressively pursued turbochargers. The federal government pursued both Korean brands after consumers complained of subpar fuel economy. Eventually, both Hyundai and Kia admitted to overstating fuel economy figures, apologized to consumers and issued mileage-based refunds to owners.
All automakers have come under extra scrutiny lately for the way they test and report fuel economy figures. The federal government sets guidelines, but it ultimately leaves testing up to automakers.