The Cadillac STS and STS-V are able and quick enough to please many buyers, but they fall a bit short of the high marks set by the German sedans in their class.
As it did in 2009, the 2010 Cadillac STS is offered in three distinct performance versions. The base STS churns away with a 3.6-liter, 302-horsepower, direct-injection V-6 mated with a six-speed automatic. From there, Cadillac offers a 4.6-liter, 320-hp V-8 teamed to a six-speed automatic transmission. Both can be fitted with rear- or all-wheel drive. TheCarConnection.com's editors prefer the V-6; with it, the STS is nearly as fast as the V-8 version, and turns in much better fuel economy of 17/26 mpg, versus 13/19 mpg for the V-8. Car and Driver points out that the available 4.6-liter V-8 offers only 18 hp more, costs an extra $9,000, and gets much lower fuel economy-"it's hardly worth it," they conclude. Edmunds confirms "the STS V-6 is basically as quick" as the STS V-8. Kelley Blue Book agrees, finding that, in real-world driving, the V-6 STS's "fuel economy proved surprisingly good, especially on long highway trips." Both this V-6 and V-8 shift gears through a six-speed automatic transmission that Edmunds observes is "slow to downshift." Cars.com notes that the transmission of the 2010 Cadillac STS offers a "manual-shift mode, but like most it takes a moment or two to induce a shift," and if "the computer thinks the car needs a downshift, it's quick to override any actions to the contrary."
In either the base or mid-line V-8 versions, the STS handles cleanly, with good steering feel and feedback. Both models have a rather firm ride, but thanks to the standard Magnetic Ride Control, which can make almost instantaneous adjustments to damper firmness, ride comfort is quite smooth. The now-defunct Forbes Autos reports of the carryover STS, "all versions deliver a fairly smooth ride with reasonably sporty handling." Kelley Blue Book says that the "STS tracked brilliantly in tight turns, though the steering response was somewhat soft and slow to react." With MRC, the "Touring" mode provides a "cushy ride and composed handling," while "Sports" mode is "a little sharper and a bit stiffer," contends Edmunds, which reports that the car handles just fine in Touring mode. On all but the base STS with all-wheel drive, Cadillac offers a handling package that adds 18-inch chrome wheels, Michelin summer tires, and Brembo four-piston brakes. ConsumerGuide finds that "reassuring brakes provide short, straight simulated panic stops."
At the far end of the performance spectrum sits the very rare STS-V and its hand-built 469-hp, supercharged V-8. It is rear-drive only, and Cadillac claims it can vault to 60 mph in less than 5.0 seconds. With the STS-V, there's overwhelming power on demand. As Edmunds reports, "Just dip the throttle and go. Mash the pedal and the STS-V jets forward on a huge wave of supercharged torque." Cars.com appreciates the way the "supercharged Northstar engine teams with a six-speed automatic transmission," calling this Caddy "an excellent example of a high-performance car that is more than livable in day-to-day driving." Automobile has qualms with the STS-V's six-speed automatic, noting it "doesn't always transfer the engine's goods to the rear axle as smoothly as you would expect, whether it's in fully automatic mode, on the sport setting, or in manual-shift mode, when it has an especially difficult time with the two-three upshift." Edmunds also observes the gearbox "has a tendency to move slowly through gearchanges."
The STS-V gets bigger wheel-and-tire combinations, stiffer suspension settings, faster-feeling steering, and Brembo brakes, and with them, the STS-V is clearly the most exciting big Caddy to drive, with tenacious grip and playful rear-drive handling to complement its powerful V-8. Edmunds feels the weight puts the STS-V at a disadvantage compared to the best BMWs and Benzes; its "rather large size ultimately limits its ability to hustle through corners, but it generally handles like a much smaller car," they insist. "Compared to the M5, the STS-V is softly sprung for American tastes, but body roll is well controlled, and the big Caddy never feels floppy or sloppy." Automobile wishes for something a little more Germanic, as it says the STS-V is "missing the fluidity that eludes so many GM products but which is usually present in the best performance cars from, you guessed it, Europe." As for fuel economy, the EPA estimates the STS-V at 13/19 mpg, while ConsumerGuide observes 13.7 mpg in mixed driving. Premium gasoline is required.