It's been a while since we last spied a BMW 4 Series coupe prototype. This time it was caught winter testing with an Audi A5 – one of its main competitors – looking strikingly similar to the 4 Series coupe concept BMW unveiled at the 2013 Detroit Auto Show back in January, most notably in the front end. The camouflage is doing a fine job disguising the taillights and headlights, but certain exposed details offer insight into the new car.

For instance, the exhaust tips indicate the test mule is being powered by a 3.0-liter turbocharged inline-six that currently resides in the 2013 BMW 335i coupe: the car the 4 Series will succeed. The German carmaker will also use its latest four- and six-cylinder units, including a new 240hp 2.0-liter four-pot gasoline engine. Given that BMW is testing it in the snow, it's also fair to assume engineers are testing the xDrive all-wheel-drive system with the A5's Quattro acting as a benchmark. Then there's the front fenders' functional air vents that BMW dub "Air Breather" and "Air Curtain."

These are said to enhance aerodynamics by routing air from the intakes to the outside of the front wheels. The BMW 4 Series coupe is expected to arrive later in the year, so we'll have to wait until then to see how much of the concept's styling is carried over to production.