The 2014 Cadillac ATS is one of the better models for fuel economy in this class of sport sedans, but it isn't the efficiency leader.
The base 2.5-liter four in the ATS is rated at 22/32 mpg, with the turbocharged 2.0-liter four earning the same ratings. At the other extreme, V-6 models earn 19 mpg city, 28 highway, or 18/26 with all-wheel drive.
Turbocharged 2.0T models stand in the middle, with ratings of 21/31 with rear-wheel drive, or 20/30 with all-wheel drive. Those numbers are a bit below those of the BMW 328i, which also includes stop-start technology, a potential fuel-saver in sluggish commuter traffic. There's also Audi's latest A4, with an eight-speed automatic--rated at 24/31 mpg.
A diesel version of the ATS is still a possibility for the U.S. market, but Cadillac hasn't yet announced a time frame for its introduction.