Mercedes-Benz gets credit—or blame—for inventing the whole silly “four-door coupe” thing with the CLS550 it launched in the U.S. in 2005. It took Audi and BMW a while to catch on, but today the notion of a sleeker but less functional four-door is so common that it has even spreaded to, heaven help us, the SUV segment. So it probably irritated the three-pointed-star team no end to see the second-generation CLS finish behind the less expensive and less powerful Audi A7 in a comparison test shortly after the new Benz arrived.

Back then, the CLS550 was the entry model—its turbo V-8 gave it a clear straight-line performance advantage over Audi’s supercharged V-6, but it lost far more points by being extraordinarily expensive, too cramped, and thirsty for fuel.

For 2015, M-B added a model at the lower end of the range, the CLS400. Using a twin-turbo V-6 in place of the V-8, it’s aimed more squarely at the Audi (and BMW’s six-cylinder 640i Gran Coupe) with a lower price, less power, and improved fuel efficiency compared with the CLS550. Sharing facelifted bodywork and a revamped interior with other 2015s, the CLS400 employs the familiar seven-speed automatic just as the 550 embraces a new nine-speed. Making Audi allusions even easier, this example showed up with 4MATIC all-wheel drive