It's hard to escape the laws of physics, but the 2008 Lexus LS 600h L does its best to try. While its German competitors power their flagship sedans with V12 engines, Lexus decided to supplement the most powerful V8 engine it has ever produced with its "Hybrid Drive" to create a powertrain equivalent to those 12-cylinder engines. As a healthy side effect, the extended-wheelbase sedan would get fuel economy equal to or better than eight-cylinder engines.

But then those pesky laws of physics come into play. The myriad hybrid components like battery packs and electric motors add about 700 pounds to the LS, and that effectively negates any performance advantages the equivalent of 438 horses may theoretically have. In our testing, the LS 600h posted pretty much the same acceleration time as the long-wheelbase LS 460. And according to EPA estimates, the hybrid sedan's fuel economy is actually 2 mpg worse on the highway. It is 4 mpg better in the city, which could be good for urban dwellers, but that fuel economy improvement would take forever to transform into money savings, considering the LS 600h L's price premium. Of course, if you're really interested in fuel economy, purchasing six-figure luxury sedans of any kind is probably not the best course of action.

While the LS 600h L fails to deliver on its V12 performance claims and fuel economy expectations, its list of standard equipment challenges a Tolstoy novel for length. Most of the options available on the LS 460 are standard on the flagship LS 600h L, with the lone options being Lexus' much-heralded self-parking feature, radar-guided cruise control and several insanely luxurious rear-seat packages. These features are backed up by meticulous Lexus craftsmanship and interior controls that, while busy-looking, are intuitively easy to learn how to operate.

Only 2,000 Lexus 600h L sedans will be sold in the United States in 2008, and it's likely all of them will easily find buyers interested in this model's high-tech charm, ultra-luxurious amenities and the cachet of its hybrid badge. Considering its less-than-stellar performance and fuel economy, though, we suggest taking a close look at the 12-cylinder Audi A8 W12, BMW 760iL and Mercedes-Benz S600 before signing on the dotted line.

The 2008 Lexus LS 600h L is a full-size luxury sedan. It's available in long-wheelbase format only. As the flagship Lexus, just about everything you could ever want on a car and even stuff you couldn't imagine being in a car are included. Standard equipment includes 19-inch alloy wheels, LED projector headlights with washers, keyless ignition, power door closers, parking assist with a backup camera, leather trimmed seats and instrument panel, a heated steering wheel, a 16-way power driver seat and a 12-way passenger seat, heated and cooled front seats, heated rear seats, per-tire pressure display and Bluetooth. The standard navigation system is run by a 30GB hard drive that can record memos from occupants and store MP3 files on the 19-speaker Mark Levinson audio system. The audio system also features a six-disc CD/DVD changer, satellite radio and an auxiliary input jack.

There are three options packages. The Premium Package includes cooled rear power seats that recline and include a center console limiting total capacity to four people. This package also includes rear-seat side airbags and the Lexus advanced parking system that allows the car to parallel-park itself. The Premium Package II includes all those items and adds four-zone climate control, a rear-seat entertainment system and power rear door shades. The Executive-Class Seating Package II adds to the previous packages with a power recliner and massage feature for the right rear seat, a rear-seat wood table and 18-inch nine-spoke wheels. The only major stand-alone option is adaptive cruise control with a pre-collision safety system.

Like other Toyota or Lexus hybrid vehicles, the LS 600h L is a full hybrid, meaning it can operate in all-electric mode at lower speeds. It also features the usual attributes of regenerative braking and electrically powered air-conditioning. The gasoline engine is a 5.0-liter V8. Alone, it makes 389 horsepower. When combined with the hybrid system, total maximum output is 438 hp.

Power coming from the V8 and electric drive motor is sent through a continuously variable transmission (CVT) and an all-wheel-drive system. The CVT has automanual shift control and three modes designed for different driving conditions -- normal, power and snow. Lexus claims the 600h L can do zero to 60 mph in 5.5 seconds, but in our performance testing we recorded a time of 6.0 seconds, a tenth of a second slower than the last LS 460 L we tested. Fuel economy is 20 mpg city and 22 mpg highway, which is 4 mpg better in the city than the regular LS but 2 mpg worse on the highway. One upside: The hybrid LS is a Super Ultra Low Emissions Vehicle (SULEV), whereas non-hybrid LS models are rated just ULEV.

The full-size 2008 Lexus LS 600h L comes with a vast array of safety features, including traction and stability control, front-seat side airbags, full-length side curtain airbags and front knee airbags. Rear-seat side airbags are optional. When equipped with adaptive cruise control, a pre-collision feature optimizes the car's safety systems for an impending impact.

Maximum quiet and comfort classify the Lexus LS more than anything else, and the hybrid version ups the ante even further. The 600h's ability to accelerate up to around 20 mph using electric power only can make this huge luxury sedan seem almost eerily quiet in traffic. Even with its air suspension set to Sport mode, the LS 600h L is still a softly sprung car with comfort being of paramount importance. Similarly, the electric power steering is accurate enough, but it's numb and doesn't offer much feedback. Those looking for a big sedan that's even remotely sporty should look toward the German competition instead. But for those in search of a comfortable cruiser that's so quiet it wouldn't wake an insomniac, the 2008 Lexus LS 600h L is an excellent choice.

In an ergonomic sense, the cockpit layout of the 2008 Lexus LS 600h L is near perfection. There's no great learning curve required to operate the climate, audio, navigation and other systems, which are controlled both by physical buttons and a touchscreen. Further, the Optitron electroluminescent gauges are both handsome-looking and effective. The rest of the interior is just as brilliant in an aesthetic sense.

As is typical with the LS series, rich wood trim is complemented by perforated leather upholstery. From the exquisite stitching in the leather to the matching of the wood grain, the fit and finish is without peer. When equipped with any of the options packages, the rear seat rivals the Rolls-Royce Phantom for passenger comfort and space. Trunk space is a serious issue with the hybrid LS, however, as the hybrid components and the optional rear seat climate control system drop capacity to a middling 11.7 cubic feet. By comparison, that's 2 cubes less than a Toyota Yaris'.