But despite the marketing for turbos' high fuel economy, the numbers in the real world often fall short.
For instance, the Dodge Dart with its 1.4-liter turbo engine carries a highway EPA rating of 39 mpg. But the Dart scored lower than 39 mpg in a recent test by Car and Driver magazine, whose editors attached a fuel meter to the car to take precise measurements of fuel economy.
"At 75-mph Texas-interstate speeds and with the air conditioning running, the onboard computer showed an average of only 33 mpg. To get near 40 mpg would take more patience and slower speeds than we're prepared to suffer," according to the magazine.
"When people think of turbos, they think of performance, but the faster you drive, the worse the fuel economy," says Mike Omotoso, senior manager of powertrain forecasting at LMC Automotive.
Consumer Reports recently tested 11 turbocharged vehicles from seven automakers to see if the vehicles delivered on fuel economy claims. The combined city-highway fuel economy for all of the vehicles came in lower than the EPA estimates by a few miles per gallon.
In addition, consumers typically pay at least $1,000 more for a turbocharged engine. So, buyers not only pay more but are likely to get lower fuel economy than with a regular engine, the magazine concluded.
Moreover, in some cases nonturbo engines can get higher fuel economy than turbocharged engines.
Honda quietly dropped the 2.4-liter four-cylinder turbo engine in the 2013 Acura RDX and replaced it with a bigger nonturbo engine that gets better fuel economy. The turbo engine, EPA rated at 19 mpg city/24 highway/21 combined, was replaced by a 3.5-liter V-6 that is EPA rated at 20 mpg city/28 highway/23 combined.
The editors at pickuptrucks.com put two Ford F-150s in a towing test, one with the V-6 EcoBoost twin turbo engine, the other with a 5.0-liter V-8. They got better fuel economy with the larger engine, 9.4 mpg for the V-8, compared with 7.2 for the V-6 EcoBoost.
In online forums, many buyers of vehicles with turbocharged engines say they are satisfied with their fuel economy. But some are grumbling.
On Green.Autoblog.com, one turbo-charged Cruze Eco owner wrote that his fuel economy has varied from 29 mpg highway in cold weather to 35 mpg, lower than the car's 39 mpg highway rating. But another owner tested his car extensively on the same roads at the same speeds and claims his Cruze achieved 47 mpg.
Industry analyst Jim Hall of 2953 Analytics in suburban Detroit says that the EPA window label number is frequently inaccurate. Calculating accurate real-world fuel economy figures that apply to most drivers of turbo vehicles, Hall said, is like asking: "How much does a bag of groceries cost?"
On F150forum.com, an EcoBoost F-150 owner named Detox wrote, "I get 17 city and 20 highway with light foot. Real driving, I get between 15 city and 17 highway mpg." The F-150 EcoBoost, the top-selling turbocharged vehicle in the United States, is EPA rated at 16 mpg city/22 highway.
Tkevin1 wrote on Edmunds.com: "I purchased a truck with the EcoBoost engine a couple of months ago and am now approaching 3,000 miles. I have had zero issues and in mixed driving have averaged around 19 mpg and have gotten as good as 24 mpg at 75mph on the interstate."
Ford spokesman Mike Levine says F-150 customers are satisfied with turbos. "Fuel economy is the top purchase consideration for EcoBoost customers," he says. "Data we have indicates that of all F-150 drivers, those with EcoBoost engines are most satisfied with their fuel economy, rating themselves 'very satisfied.' In fact, F-150 leads fuel economy satisfaction among all light-duty, nonhybrid pickup truck customers."
Ford has been the most aggressive with turbos. About 80 percent of its North American nameplates are available with an optional EcoBoost engine, which combines a turbocharger with direct fuel injection and other technologies.
Ford has sold more than 600,000 vehicles in North America with small turbocharged engines under its EcoBoost brand name. More than 400,000 of those have been one model, the F-150.