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We regret to inform you that the era of the V8-powered midsize luxury sport sedan could be over. Gas prices aren't the problem; instead, it's the impending federal fuel-economy standards that could spell the end of these luxurious street sleepers.

So this meeting of the 2008 Audi A6 4.2, 2008 BMW 550i, 2009 Jaguar XF Supercharged and 2008 Mercedes-Benz E550 might represent the end of an era.

Under the new rules, shoving big V8s into midsize sedans will become a questionable prospect even for luxury brands. Without massive price increases, only the most expensive flagship models will be able to offer thirsty eight-cylinder engines, leaving the smaller sedans to get by with six cylinders or worse.

With that prospect looming, we figured a comparison of the current crop of V8 midsize European luxury sedans was in order. They may not have much of a future, but they offer some of the best combinations of luxury, prestige and completely unnecessary horsepower you can get — for now.

Hope You Like the Germans
Comparing overpowered luxury sport sedans usually involves several Germans; in this case there are three. There's the 2008 BMW 550i with its 360-horsepower 4.8-liter V8 and the only manual gearbox that's available in this segment. It is a six-speed, of course, and although we would have preferred a six-cog automatic to keep our comparison equitable, our test car's stick shift proved to be a constant reminder of BMW's dedication to hard-core enthusiasts. This 550i's $69,820 sticker price is also a reminder that BMWs don't come cheap.

Then there is the 2008 Mercedes-Benz E550, a relative bargain at $63,970. There's definitely no manual available, but its automatic does use seven speeds to get the most out of the car's 382-hp 5.4-liter V8. And like the 550i, the E550 puts the power to the ground through its rear wheels.

The 2008 Audi A6 4.2 comes standard with all-wheel drive, so what it lacks in burnout potential it makes up for in all-weather capability. Still, its 4.2-liter V8 sends 350 hp through a six-speed automatic transmission, so the A6 is still a formidable sport sedan. Add the S line package and 19-inch wheels like on our test car and it doesn't look half bad either. This A6 is also the least expensive sedan in the test at $63,515.

Rounding out our foursome is the all-new 2009 Jaguar XF Supercharged, a replacement for the S-Type sedan. The XF's supercharged 4.2-liter V8 is essentially the same engine used in the previous S-Type R, though it has been bumped to 420 hp. It uses a six-speed automatic transmission and sends its power to the rear wheels. There are only three options, and ours had two of them, pushing the final price to $65,475.

In Their Element
With their powerful V8s, sport suspensions and big wheels and tires, these four sedans have the muscle of serious performance cars. But as capable as these sedans are, their real mission is comfortable commuting and the occasional long-distance trip.

We kept that mission in mind as we racked up seat time over the course of two weeks. Sure, we ran them hard on twisty back roads, but we weren't expecting any of them to remind us of a Lotus. Numbers still matter, though, so we track-tested them, too.

More important, these cars have to make broken concrete highways feel as smooth as the autobahn while keeping the cabin quiet in the process. We expect all the usual high-end features as well — navigation systems, premium stereos and cabins that look like they belong in $65K sedans. Each of these cars represents premium transportation, more like an executive jet than a commute-hour slogger.

When it was all done, there was a clear winner, and it wasn't the car we expected.

1st Place: Jaguar XF Supercharged
This is no fluke. The Jaguar XF beat the 2nd-place BMW 550i by nearly 11 points. Whether it was overall performance, features, price or our editors' own recommendations, the Jaguar came out on top. Here's why.

It puts up impressive numbers — even at 4,200 pounds. That's nearly as much as the Audi (4,225 pounds) and roughly 200 pounds more than the BMW or the Mercedes, yet the XF is quicker through the quarter-mile than the BMW and only a couple tenths behind the Mercedes from zero to 60 mph.

Through the slalom, the XF is the fastest sedan of the four thanks to quick steering and loads of grip from its 20-inch Pirelli P Zero tires. It is the second grippiest on the skid pad (0.87g), and turned in the shortest stopping distance of just 108 feet.

Even with all this dynamic capability baked in, the XF isn't a hard-edged sport sedan. There's noticeable tension between the car and the pavement, but it doesn't translate into sharp jolts or jittery handling on the highway. Shifts from the six-speed automatic are quick but smooth, and there's almost no whine from the supercharger. If anything, the big V8 is a little too tame at times, leaving the XF feeling deceptively slow off the line during acceleration.

Getting the most out of the XF requires dialing up the Dynamic Drive program and the transmission's Sport mode. The quicker shifts and more responsive throttle cure much of the V8's sluggishness and make the XF feel anxious to go fast. It's up to the task with a thick-rim steering wheel, well-placed shift paddles and a supportive driver seat.

Return to the standard settings and the XF reverts back to a relaxed, long-distance cruiser that's easy to get along with. It might have all the latest gadgets, but the XF never overwhelms you with its technology. Most of the more complex controls are accessed through the dashboard touchscreen, while the climate and radio controls use traditional knobs and buttons.

It makes for a simplified and tasteful center stack design. Combine that with the XF's nicely detailed gauge cluster, polished wood trim and otherwise bright cabin, and the German sedans look sterile in comparison.

Passenger space in the XF isn't a problem, despite its low, sleek roof line. The XF even has the largest trunk of the group, although its small opening limits its usefulness.

There are other minor issues as well. Some of the knobs that look substantial actually feel flimsy, and although the steering wheel paddle shifters work well, they're made of plastic. Not good when you consider that Mitsubishi uses magnesium paddles in its $20,000 Outlander SUV.

Small issues aside, the 2009 Jaguar XF Supercharged is exactly what a sedan in this category should be. Fast, comfortable, well-sorted on the highway and agile when pushed, the XF is easy to live with, regardless of the circumstances. Sure, gearheads might appreciate the BMW's dedication to performance, but the Jaguar XF is a better overall package.

2nd Place: BMW 550i
Losing by 11 points to the Jaguar XF makes it look like the BMW's better years are behind it. Don't believe it. The 550i is still one of the best built, sharpest-handling sedans on the road today. But there are aspects of the 550i that could use an upgrade, and given that the Jaguar costs less and offers more both on the track and off, the 5 Series couldn't keep up.

It's still near the top of its class when it comes to performance, as the 550i beats the Jaguar from zero to 60 mph, but then it falls behind by the end of the quarter-mile. Its sport suspension with active roll stabilization delivers the best number on the skid pad of this group (0.89g), but the same setup makes this car hard to get through the slalom cones, leaving it slower than the Jaguar by nearly 2 mph. The BMW's 111-foot stop from 60 mph is the second shortest of the group after the XF.

On the street, the 550i is still the sedan to have when the road is right. It delivers better road feel than the XF and the brakes are easier to modulate. The roll stabilization system takes some getting used to, but ultimately it makes for a highly predictable chassis when you're having fun. Of all the sedans in the test, the 550i is the one that will make you feel like a better driver.

It's on less challenging roads where the BMW loses some of its luster. The suspension isn't rock hard, but there are times when you wish for softer bushings to take the edge off rough highways. This compromise is barely noticeable at first, but then you get into the XF and realize how supple the Jaguar feels over the same roads. No doubt the BMW's 19-inch wheels and tires contributed to its stiff-legged performance, but it's no excuse, since the XF wears even larger 20-inch tires.

The 550i fell further behind the Jaguar the more time we spent behind the wheel of the two cars. BMWs have never had the cheeriest of cabins, but the XF makes the 550i's cabin look especially sullen. Sure, the BMW offers very legible gauges and good-quality materials — not to mention minimal clutter thanks to iDrive — but for $70K this car is still a little plain. With more interesting colors and fewer options to keep the price down, the 550i would have finished closer to the XF.

Also consider this. The 2008 BMW 550i is the top pick when it comes to the personal choice made by our editors. Some of this popularity can be chalked up to its manual transmission, a rarity when it comes to V8-powered sedans. It's not the whole story, though, as the 550i is simply a formidable sport sedan, a real driver's car despite its uninspiring interior furnishings. If you can afford the premium and the Jaguar still looks soft to you, the BMW 550i is one of the best of this dying breed.

3rd Place (tie): Audi A6 4.2
As the least expensive car in the test, the 2008 Audi A6 4.2 started out ahead. Unfortunately for Audi, it never got any better for the A6. Weak overall performance is its biggest downfall, both on the track and off. Add in a short list of features and a choppy ride and the A6 never challenged for the lead in our comparison.

With the optional sport suspension and 19-inch wheels and tires, our A6 test car has all the hardware necessary to compete with the big guns — at least in the suspension department. Under the hood, its 4.2-liter V8 delivers the least amount of horsepower while carrying the most weight.

These handicaps showed at the test track, as the A6 isn't even in the same league as the other three cars when it comes to acceleration. It's a full second behind the Jaguar from zero to 60 mph and in the quarter-mile, while the A6 also turns in the third-longest stopping distance from 60 mph at 114 feet.

Sticky tires and full-time all-wheel drive help redeem the A6 in the slalom and on the skid pad, as it is the second fastest through the cones behind the Jaguar and only slightly less capable on the skid pad with an 0.86g performance.

So it is no track star, yet the A6 didn't feel much better on the street, either. It has the same heavy, buckled-down feel as the 550i, yet it lacks the BMW's precise connection with the road. The Audi doesn't shift its weight with the same predictable control as the Jaguar from corner to corner, and the power is just adequate.

The Audi's lack of agility would be understandable if it rode like a Lexus around town, but it's just the opposite. Rough highways are miserable, as the Audi crashes and hops over every crack and ripple in the pavement. It's hard to imagine there's an even more aggressively tuned RS6 on the horizon, as this example of the A6 couldn't ride much worse.

From an interior design standpoint, the A6 4.2 sits roughly between the XF and the 550i. Its cabin has the same serious character as the BMW, although it's matched by a similarly impressive level of build quality. Audi's MMI user interface is also far more intuitive than iDrive, so there's less frustration with basic tasks like changing the radio station.

As nice as it looks and feels on the inside, the 2008 Audi A6 4.2 doesn't deliver on the V8 experience. This engine is too quiet, too slow and too rough around the edges to drive every day without considering the other three sedans first. Even if you need all-weather traction, the E550 offers all-wheel drive, so the Audi isn't the only game in town anymore. Although nice-looking and well built, the A6 is a better prospect as a sport sedan with a V6 and a much lower price.

3rd Place (tie): 2008 Mercedes-Benz E550
The Mercedes-Benz E550 might have earned the same score as the Audi, but they're two very different sport sedans. Instead of a weak motor and a punishing suspension, the E550 leaves every other car in its wake at the drag strip while delivering a pillow-soft ride everywhere else. If you're looking for an elegant, comfortable sedan that will shorten highway on-ramps with shocking speed, the E550 is your sedan.

With the largest V8 (5.4 liters) of this group and the most gears (seven) to play with, the E550 posts some pretty impressive acceleration numbers. It beats the BMW and its six-speed manual by 0.2 second from zero to 60 mph and has a similar lead on the XF at the quarter-mile with a pass of 13.4 seconds. That's fast enough to dust off a sizable group of sports cars, let alone high-dollar luxury sedans.

The fun ends at the drag strip, however, as the E550's suspension isn't nearly as capable as the drivetrain. Even with the air spring suspension dialed to its firmest setting, the E550 still feels heavy and detached compared to the buttoned-down chassis of the BMW and Jaguar. It's the slowest through the slalom (62 mph) and has the least amount of grip on the skid pad (0.82g) and the longest 60-to-0-mph braking distance (120 feet).

On the flip side, once the Airmatic suspension is reset back to its standard setting, the E550 has the softest, most forgiving ride off the track. If you like plenty of wheel travel and a hint of float on the road, the Mercedes is the choice here.

That said, the XF is nearly as comfortable over rough pavement and it never feels like it has lost contact with the pavement like the Mercedes. Add in the E550's noticeable dead spot on-center in its steering action, and the E550 simply doesn't feel like a real sport sedan regardless of how fast it goes in a straight line.

There's nothing sporty about the interior, either. The seats don't grab you like the BMW and the gauge cluster dedicates a third of its space to a clock. Build quality is excellent, though, and the trim looks fit for a car in this class. It's a traditional layout with a few electronic gadgets thrown in for good measure.

An all-new E-Class is headed our way next year, and it will no doubt have a chassis more capable of dealing with 382 hp. For now, the 2008 Mercedes-Benz E550 is a luxury sedan first and a sport sedan second.

Final Thoughts
At this level of price and performance, the differences between luxury sedans get harder and harder to define. They're only tenths apart at the track and a few decibels away from each other on the freeway. The numbers still say a lot, but in the end we also ask ourselves which car we would recommend to prospective buyers in the category.

In this test, it was the Jaguar XF that grabbed the most recommendations. Call it backlash against the old guard if you want, but the XF does all the things the Germans can without feeling so serious about it. You get in the car and there's some occasion to it, and no matter where you drive, it lives up to the promise of its price tag.

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