Comparison Test: 2008 BMW M5 vs. 2009 Cadillac CTS-V vs. 2009 Mercedes-Benz C63

Once you get your hands on a supercharged 556-horsepower 2009 Cadillac CTS-V, you know that you need a 500-hp 2008 BMW M5 with which to measure it. It's a matter of practical science.

Of course, there's a sizable price difference between the $59,995 CTS-V and the $86,675 M5, and we don't want to get our comparison results skewed by mere money. Maybe we should add the 507-hp 2009 Mercedes-Benz E63 AMG to our science project. Trouble is, this Merc's $86,875 price tag still doesn't put the CTS-V under any pressure.

We had a better idea. We opted for the more nimble 2009 Mercedes-Benz C63 AMG. This compact sedan cranks out only 451 hp, but it weighs almost 400 pounds less than the E63, and its base price of $58,075 rings up about $2,000 cheaper than the CTS-V.

Is the 2009 Cadillac CTS-V a true benchmark in the super sedan category? Measured against the pure performance of the 2008 BMW M5 and the value of the 2009 Mercedes-Benz C63 AMG, we knew the truth would come out.

The Fast-Moving Blue-and-White Target
Cadillac frankly admits that the target for the new CTS-V is the BMW M5, as the blue-and-white roundel has been the bull's eye in this super sedan category since the E60 version of the M5 was introduced in 2004. Say what you will about its SMG automated manual transmission and its iDrive cockpit controller, but there's nothing like the warble of its 500-hp V10 or the athleticism of its chassis. This M5 always manages to perform better than the sum of its parts would suggest.

The M5 has also changed the way car owners in this category think. One of us learned this recently while stopped in a left-turn lane with the M5. A friendly horn toot drew his attention to a brand-new, black-on-black 2009 Mercedes-Benz C63 AMG. Our man expected some kind of fraternal salute from the AMG, as a meeting of two such cars is pretty special, even in Los Angeles. You know, that cool little lift of the chin that rich guys affect.

Instead, the Merc driver casually flipped off our man with a smile and then proceeded to lay down the biggest smoky burnout with his C63 ever seen on a crowded public boulevard in the middle of the day.

So there's that, and you gotta hand it to that C63 driver. He knows that it's all about humiliating the M5 in any way you can. Either that, or our man Magrath just rubbed him the wrong way. (Magrath is like that sometimes.)

Enter the Challengers
We've already tested both the six-speed automatic and six-speed manual versions of the 2009 Cadillac CTS-V and those preliminary tests showed the V-spec's supercharged 6.2-liter V8 has plenty of straight-line performance to challenge the M5's 5.0-liter V10. The Nürburgring-tested brakes and suspension are also first-rate.

Our test car has an automatic transmission, just like the car that set a lap record at the Nürburgring, and it also has a bottom line of approximately $64,160 (official pricing is still forthcoming) thanks to the hard-drive-based navigation system, suede-wrapped steering wheel and shift knob, plus high-performance brake rotors.

We've also seen a Mercedes-Benz C63 AMG a time or two prior to seeing one etch a giant number 11 in rubber on Venice Boulevard recently. We love its snarling, AMG-designed 6.2-liter V8 and the telepathic abilities of its seven-speed automatic transmission, but have found the suspension setup that's part of the AMG Performance package too harsh for daily use.

Our C63 test car with the standard suspension has had its price pumped up with metallic silver paint, an iPod integration kit, TeleAid, the P02 Premium Package, the 318 Leather Pack and the 320 Multimedia Package for a total of $66,880.

Power
Power is wasted if you can't wield it with precision or are burdened by weight. Our calculations show that the 4,315-pound, 556-hp CTS-V with 7.8 pounds per horsepower should be the quickest car here, and so it proves to be. The M5's weight-to-power ratio is 8.3 pounds/hp and the C63 checks in with 8.9 pounds/hp in fighting trim.

The CTS-V outpaced its competitors in the sprint to 60 mph with a dominant 4.3-second performance (4.0 seconds with 1 foot of rollout like on a drag strip) supplemented by a scorching quarter-mile performance of 12.4 seconds at 114.7 mph. The next quickest to 60 mph proved to be the Mercedes with a 4.5-second tear (4.2 seconds with 1 foot of rollout like on a drag strip), while the BMW stopped the clock in 4.8 seconds (4.5 seconds with 1 foot of rollout like on a drag strip).

The three different transmissions couldn't have behaved more differently, and they definitely influenced the outcome. The M5's seven-speed single-clutch automated manual required perfect throttle/shift coordination for a decent launch, not to mention constant vigilance against redline excess while shifting as well as forgiveness for harsh upshifts. In comparison, the Mercedes' seven-speed automatic obliged consistent launches and seamless shift action, while the Cadillac's six-speed automatic makes the task as easy as the Mercedes, yet it shifts nearly as hard as the BMW.

The quarter-mile finishing order was CTS-V, C63 and M5 just as it was to 60 mph, and 0.2 second separated each car (12.4, 12.6 and 12.8 seconds, respectively). At the end of the quarter-mile, however, the M5 began to reel the others in with a stout trap speed of 115 mph compared to the CTS-V's 114.7 mph and the C63's 112.3 mph.

Poise
Getting a 2-ton car to go fast in a straight line is easy; all it takes is horsepower plus big shoes. Making it dance like a sports car is another thing entirely. Both the BMW and Cadillac come standard with driver-adjustable multimode shocks, and the M5 utilizes multivalve dampers with three distinct levels of suspension firmness.

Cadillac uses dampers with specially formulated oil that can vary viscosity within the shock absorber like a $105,000 Corvette ZR1 or $300K Ferrari 599 GTB Fiorano to cope with the demands of high-speed driving. The Cadillac's two-mode active system constantly monitors wheel motion and fluctuates between compliance and firmness in milliseconds. It works miraculously well.

The BMW has three-mode adjustment for its suspension. Only in Europe is the C63 available with driver-adjustable dampers. Even so, the taut-riding U.S.-spec C63 (without the spine-jarring $3,990 AMG Performance package) can be driven comfortably every day.

Truth be told, however, both the BMW and Cadillac performed better in their "Normal" settings, especially on the racetrack where chassis control and suspension compliance rule over brutal stiffness. Put to use on our slalom, all three cars were tantalizingly close to the magic 70-mph barrier and equally close to 0.90g on the skid pad. On paper, it was a virtual tie, but the tiebreaker would be found at the Streets of Willow road course.

Track Day for the Roundel
We strapped our VBox satellite-based data-acquisition equipment to each of the three super sedans and let the manmade stars tell us which one was quickest around the 1.8-mile Streets of Willow on a perfect day in the high desert.

With the M5's M-menu selections on maximum performance, we turned our first hot lap in the BMW with its suspension in the firmest setting, but found the car skittish through a couple of the track's undulating, high-speed corners. Knocking down the suspension firmness a notch earned a few tenths of a second. The SMG transmission functioned brilliantly on the kind of road course for which it was designed, ripping upshifts and matched-rev downshifts.

The M5 chassis behaved manageably during the four hot laps our testing protocol called for, but understeer and brakes held it back. As the notes from our logbook record, performance testing on the drag strip had turned up the tendency of the car to lose a little bit of grip as the tires heated up, while the skid pad revealed stubborn understeer at the limit.

To compensate, we reverted to one of the oldest mantras in the racer's rulebook: slow in, fast out. The problem is, this driving technique negated the M5's potential advantage in one crucial part of the track, a high-speed straightaway followed by hard, hard braking and a 90-degree corner. The VBox recorded a top speed of 104.8 mph for the M5 in this section, while the car recorded a best lap of 1:30.36, just 1 second behind the time set by the 2008 Porsche 911 — a remarkable performance for a 4,100-pound sedan.

AMG: All Mighty Goodness
Next, the C63 AMG headed out for its session.

The 4,001-pound car was noticeably more capable in the tight turns and rotated its nose adroitly not only under hard braking but also while powering out of corners. The C63 could've been driven sideways through almost any corner, but a little restraint led to a quicker lap time. The brakes were never an issue, and neither was the seven-speed automatic transmission, which earned near-identical lap times in both full-manual and sport-automatic modes.

We were able to stand on the V8's loud pedal longer in the high-speed section, reaching 104.2 mph before jumping on the unflappable brakes. What the C63 apparently lacked in horsepower, it made up for in braking and control. The result proved to be a lap time of 1:29.53, beating the mighty M5 by almost a full second.

Cadillac? Are You Serious?
Finally, it was the Cadillac's turn. Could it put it all together, or would the CTS-V prove to be a paper tiger?

As with the M5, the CTS-V's first hot lap was timed with the suspension in its firmest setting, but subsequent quicker laps were turned in the softer mode. And though the six-speed automatic has a manual mode, we found both up- and downshifts too slow to arrive and too upsetting to the chassis when they did. As former GM test-driver John Heinricy has advocated, the car's best performance came in automatic mode.

The CTS-V felt almost as if it was loafing around the track. (Not because we felt comfortable — to the contrary, the driver seat was about as supportive as a beach chair.) The supercharged V8 never sounded like it was working hard, the suspension was so good at soaking up bumps that the track felt smoother, and the transmission did all the thinking so we only had to gas-brake-turn, gas-brake-turn, and so on.

And because the maximum-strength CTS has the brakes to match its power, the Caddy flew through the speed trap at a crushing 107.5 mph and stopped on a dime for the approaching corner. Initially we weren't persuaded we had cut a very quick lap, but the downloaded data proved that the Cadillac had recorded a best of 1:29.24, some 0.29 second quicker than the Mercedes and 1.1 seconds quicker than the BMW.

Uh-oh. This is so embarrassing for the Europeans.

It's Academic
If you're looking for the short answer, here it is; the 2009 Cadillac CTS-V is undeniably faster, more nimble and between $27,000 and $32,000 less expensive than the BMW M5 it was designed to beat. The M5's price/performance ratio really penalizes it in this comparison.

Is the CTS-V really better than the C63 AMG? Well, once you look at the score cards, you'll find one 1st-place score in the M5's column (earned in our evaluation category), three 1sts for the CTS-V (features, performance and price), and two for the C63 (editors' personal and recommended picks). The winner would seem a forgone conclusion then. But have a look at the 2nd- and 3rd-place scores.

The C63 snatched four 2nd-place scores to the CTS-V's three 3rds. Because of the way we weight the final scores, the Cadillac ekes out a 1.6-point margin over the Mercedes-Benz. We've declared such close scores an effective tie in the past, but the Cadillac's dominance in measured performance tests plus its uncommon comfort, comprehensive list of features and even best observed fuel economy of this trio combine to earn it our fullest endorsement as the winner of this comparison.

"Sport Sedan Standard of the World" now wears a Cadillac wreath and crest.

The manufacturers provided Edmunds these vehicles for the purposes of evaluation.