Within the notch Chicago has punched in the nation's snow belt, two key factors lead to a luxury sedan's success: a prestige badge on the hood and all-wheel drive behind the wheels. A day of commuting along any of its salt-clogged arteries will show that, in the Windy City, quattro Audis and anything with an "X" in the name are as popular as Daleys and deep dish. German marques have twigged to the necessity of all-wheel drive for two decades, and Cadillac would have left untold sales on the table if it had sent the CTS out onto these roads without its own all-weather variant. Fortunately, Cadillac's decision makers have smartened up since the days of V-8 diesels and leather-lined Cavaliers, and the CTS4 is its answer to this demanding segment.

That this is the first all-wheel-drive CTS doesn't mean the mechanicals are new. The larger STS and the SRX crossover have been using the CTS4's electronically controlled system for about three years and, like those two vehicles, the CTS gets a 40/60 rear-biased torque split under normal driving conditions. The only difference here is that the CTS is the first model to get a new generation of Borg Warner's "TorqTransfer" computer algorithm. As a result, the car's rear-drive characteristics are mostly preserved — mash the throttle and a load of torque will jump on your back rather than pull you by the forearms. Under extreme slippage, the active transfer case can push a full 100 percent of the engine's output to either end. A rear limited-slip differential is available as part of an optional performance package, and stability control is standard.

Other than the little chrome "4" added on the trunk, nothing visually separates this CTS from the rest of the pack — it rides on the same wheels and tires and measures equally in width and height. But get in and drive, and it is immediately apparent that the CTS's performance edge has been dulled by 244 pounds of extended driveline. A numerically lower final drive ratio (3.23 vs. 3.42) hurts acceleration numbers and makes the CTS4 feel less than excited to pass the unrushed members of the driving community. More drivetrain components also mean more drivetrain power loss, so we suspect fewer of the direct-injection 3.6-liter's 304 horses actually make the trip down to the ground. The steering feels slower and heavier, too, and a quick look at the specs confirms suspicions: the CTS4 uses a relaxed 19.1:1 steering ratio while the two-wheel model's system is set at 16.1:1. Although none of this is good news for the enthusiast, Cadillac deserves credit for developing a cohesive group of controls — the car got heavier and slower so the steering and throttle have followed suit.

The all-wheel-drive CTS's liabilities relative to its rear-wheel-drive sibling fade on the open road. In exchange for its laid-back reflexes, the heavier CTS4 is able to settle into corners and stay confidently planted. Likewise, the same great dampers from the rear-driver sort out even the harshest surfaces. In fact, with power routed to all four corners and the extra weight sitting low to the ground, the CTS4 feels more surefooted than the base model through long, high-speed sweepers. But dump the car too hard into a tight bend and the plowing begins. That's because along with the CTS4's extra bulk sitting ahead of its centerline, the front stabilizer bar has been thickened by four millimeters and the rear is one millimeter thinner. For those in need of a quick handling lesson: Large front bars plus small rear ones equals massive understeer.

None of this is our way of saying, "CTS4 iz the suck LOL," because that isn't the case. But Caddy's handling sacrifice on the altar of traction means the 4 isn't the enthusiast's CTS. It's still a perfectly good luxury sedan for a target market that doesn't know about or even comprehend things like stabilizer bars and understeer. What those people do know is that stop-and-go winter traffic on the Dan Ryan is one of the most brutal forms of torture man can endure. Out there, it's the effortless grip, compliant suspension, comfortable heated seats, and great stereo that make the car a proper sanctuary from the encroaching elements. For those buyers, the CTS4 is hard to beat.