Automakers using cylinder deactivation to trick EPA?

Does real world fuel economy matter?

An article in USAToday notes that many automakers are now using cylinder deactivation to increase fuel economy.

Great news right?

"Every little bit helps. But I think it's for marketing reasons," says David Champion, director of auto testing for Consumer Reports magazine. He figures the systems are tuned to deliver their biggest benefits during the federal fuel-economy test cycle. That's the test that generates the mileage numbers posted on new vehicles' window stickers.

"We've found that in most driving conditions, it's always in full-cylinder mode, not cutoff," Champion says. "It's a sub-10% improvement, maybe 13 mpg instead of 12" on a big pickup.

Consumer Reports gets fuel-economy readings by splicing a meter into a vehicle's fuel line to "measure the exact amount of fuel consumed in three very strictly controlled tests," he says.