Three models are available.The GS 350 features a 303-hp, 3.5-liter V6 and six-speed automatic with manual shift gate.All-wheel drive is available.We found the GS 350 thoroughly enjoyable to drive.The V6 is quite responsive, propelling the GS 350 from 0 to 60 mph in an impressive 5.7 seconds and gets an EPA-estimated 19/26 mpg.

There's also a hybrid: The GS 450h combines the 3.5-liter V6 with two electric motors for improved power and fuel economy.The GS 450h hybrid is actually the quickest of the GS sedans, getting from 0 to 60 mph in 5.2 seconds.Fuel economy for the GS 450h is rated 22/25 mpg City/Highway on the government's EPA cycle.

The 4.6-liter V8 makes 342 horsepower and comes with an eight-speed automatic transmission.For added performance, the eight-speed transmission includes a Sport mode that enables you to manually make sequential shifts with the console-mounted gear lever.The GS 460 is the fastest of the models, with a top speed of 149 mph and 0-60 in 5.4 seconds.

The all-wheel-drive GS 350 AWD features a fast-acting, clutch-type center differential that sends 70 percent of the power to the rear wheels under normal circumstances to help foster the dynamics of a rear-wheel-drive car.When wheel sensors detect slippery road conditions, as much as 50 percent of engine power is diverted to the front wheels to increase the car's overall traction on the road.

The third-generation Lexus GS came to market for 2006, a showcase of Toyota's most advanced technology.It arrived with more computing power than some third-world countries and a standard of luxury usually enjoyed only in the best zip codes.Refinements followed for 2007; and then a much-improved V8 engine arrived for 2008.2008 models benefited from a new front fascia and chrome grille surround, new side-mirror turn signals, a revised instrument panel, and other appearance tweaks inside and out.There are no significant changes for 2009.

The GS 460 ($53,320) has a 342-hp V8 and an eight-speed automatic transmission.The GS 450h ($56,400) features a hybrid powertrain that combines the 3.5-liter V6 with two electric motors.It has a continuously variable automatic transmission with six preset gear ratios for the manual shiftgate.

Standard equipment on the GS 350 includes thick, regency-style leather upholstery and color-coordinated wood trim (golden or gray bird's-eye maple, or red walnut); dual-zone automatic climate control; interior air filter; power tilt/telescoping wood and leather-wrapped steering wheel with audio controls; cruise control; heated 10-way power-adjustable front seats; memory for the driver's seat, mirrors and steering wheel; trunk pass-through; heated auto-dimming power exterior mirrors with tilt-down back-up aid; power windows; power locks; SmartAccess keyless access and starting; sunroof; remote engine starting; 10-speaker AM/FM/cassette stereo with six-disc CD changer; auxiliary audio input jack; vehicle information system with a seven-inch touch screen; Bluetooth wireless cell phone link; auto-dimming rearview mirror; universal garage door opener; power trunk closer; automatic HID headlights; theft-deterrent system; fog lights.The GS 350 comes with P225/50WR17 summer tires on alloy wheels; the GS 350 AWD has P225/50R17 all-season run-flat tires.

The GS 460 adds heated and ventilated front seats, adaptive headlights, an adaptive variable suspension with sport and normal modes, a faster (and variable) steering ratio, bigger front brakes, and P245/40ZR18 summer tires.

The GS450h gets front and rear park assist, rearview camera, rain-sensing wipers, power rear sunshade, and headlight washers.It loses the trunk pass-through, but share's the V8 models P245/40ZR18 summer tires.

Options include a navigation system with voice recognition ($1,850) which includes a rear backup camera; front and rear park assist ($500); Mark Levinson 330-watt audio system with 7.1 surround sound, DVD Audio playback, and integrated navigation and backup camera ($3,630); active vehicle stabilizer system for 460 ($3,000) or 450h ($3,320); adaptive variable suspension ($620); pre-collision braking system with radar-type cruise control ($2,850); Lexus Link road assistance ($900); rain-sensing wipers with headlight washers; power rear sunshade ($210); ventilated front seats ($200); all-season run-flat tires; and a rear spoiler ($200).

Safety features that come standard include dual front air bags, front and rear side airbags, driver and front passenger knee airbags, curtain-type head-protection air bags both front and rear, and a tire-pressure monitor.Front and rear park assist and a rearview camera are standard on the GS 450h and optional on the other models.Active safety features that come standard include anti-lock brakes with electronic brake-force distribution and brake assist, traction control, and electronic stability control (ESC).The GS 460 comes with Vehicle Dynamics Integrated Management, an ESC system that processes steering angle, yaw rate, deceleration, brake pressure and wheel speed, and then uses the car's entire range of electronic controls for the engine, brake, and steering controls to help the driver control the car in an emergency handling situation.In contrast to conventional ESC systems, which react to a car's loss of control, VDIM has been developed to anticipate a dangerous situation, and then by making certain corrections, allow the driver to continue without even realizing the system is at work.The available Lexus pre-collision system uses a radar sensor to detect the onset of a collision and will automatically optimize chassis calibration for quick steering response, retract the front seatbelts, initialize brake assist and even decelerate the car at 0.3 g if the driver fails to take avoiding action.

The GS expresses simplicity, yet the car is thoroughly sculpted throughout its length.The design is perhaps a little predictable, yet the combination of this sleek shape and careful work to reduce aerodynamic turbulence beneath the car has produced a remarkably low 0.27 coefficient of aerodynamic drag, and this promotes a quieter interior and fuel efficiency.

For 2008, the front fascia was reworked with a flatter front bumper, a slightly revised lower air intake, and a chrome grille surround.The side mirrors got turn signals, and the wheel designs were new.

The GS has high-intensity-discharge headlights with an available system that automatically compensates headlight aim for different passenger loads.The power-adjustable mirrors have defogging heat elements and tilt down when the car is in reverse.The available variable intermittent windshield wipers actuate automatically when raindrops are sensed.Fast-acting LEDs are used in the rear brake lights.Big 18-inch wheels are available.

The tilt/telescoping steering wheel is handsomely trimmed in wood and leather.In the traditional Lexus style, the instrumentation is set deep within the dash to promote easy focus by older drivers and also features electroluminescent instrument needles for heightened visibility.Across the dash panel, each gauge, button, knob, lever and wheel is clearly identified by easily read words or symbols, so you can intuitively grasp the meaning.There's soft-touch electronic actuation for virtually every control, from the window switches to the trunk release.

Dominating the center stack is a seven-inch electronic screen with touch-screen controls.Two banks of menu buttons flank the screen.The driver uses this screen to operate the audio system, climate control, and optional navigation system with backup camera, though many functions are duplicated with nearby buttons on the dashboard.Navigating through the submenus doesn't take too much brainpower, but like most multi-tasking electronic systems, a day spent with the owner's manual on a quiet side street is the best way to figure out the way to work everything properly.

Lexus has made a quality audio system a key component of its brand identity, so it's no surprise that the GS sedan has a premium system.The standard 134-watt system features an AM/FM tuner with cassette tape and an in-dash, six-disc CD changer.It plays through a 10-speaker sound system.An auxiliary audio input jack is provided, and now accepts both MP3 and WMA formats.Audiophiles can opt for the Mark Levinson Premium Surround Sound system, developed especially for the GS interior.Utilizing 5.1 surround sound playback via a 7.1-channel speaker topology, its 330-watt amplifier sends the vibes through 14 speakers via 11 channels of amplification.It even plays DVD movies on the seven-inch screen when the car is parked.

The DVD-based navigation system has information for more than 6 million points of interest, while route searching is conducted at ten times the speed of previous-generation systems.The screen has excellent resolution and the map images have three-dimensional shading to aid recognition.Voice recognition makes the system a hands-free experience for the experienced user.

The Bluetooth-compatible telephone system can be operated by voice command or through the seven-inch touch screen.

Intuitive Park Assist considers steering angle input as well as the usual distance-warning sensors to offer contact avoidance advice through graphics in the dashboard-mounted information screen.This advice also is displayed in the lower center of the speedometer, an area that is also used to show information from the trip computer, radar cruise status, distance monitoring and various warning messages.This system is the last word in ding prevention in the supermarket parking lot.

The combination of the 10-way power-adjustable driver's seat and a thick-rimmed steering wheel with an electrical tilt/telescopic control helps you find a comfortable driving position.The driver's seat itself is sculpted with an extensive set of bolsters that support you, though they are not so restrictive that they encumber easy ingress and egress.Despite the multiple controls, one of our test drivers didn't like the seating position because the front of the seat bottom doesn't tilt upward.And tall drivers might not like the GS at all, because head room is limited.

The same goes for the back seat.Both head and leg room will be tight for anyone over 6 feet, 2 inches, and the front seats have little toe room if the front seat is at its lowest point.The seat is comfortable, however, and a center armrest folds down to reveal the pass-through.That pass-through is handy, but not as handy as a split-folding rear seat, which the GS doesn't offer.

The trunk is relatively small, measuring 12.7 cubic feet in volume.And the trunk opening is small, caused by the short overhang.The GS does not excel at cargo capability.

The available 18-inch tires can make the ride a bit harsh, however.In our test of a GS 460 on Chicago streets, the suspension reacted harshly to sharp potholes, sending the types of sounds into the cabin that make you feel like you're in danger of popping a tire or doing suspension damage.

The GS can rip down the road if you like.Wide tires furnish plenty of cornering grip: P245/40ZR18 tires are standard equipment for both the GS 450h and GS 460, while the GS 350 carries P225/50WR17 tires.

The base suspension geometry provides good handling, while gas-charged dampers and coil springs promote a resilient, long-legged ride.The GS 450h and GS 460 both have two-position, electronically adjustable damping control to help the car adapt to driving conditions, as well as available Power Active Vehicle Stabilizer, which minimizes body roll during fast driving and further enhances the sensation of effortless speed.

The high-tech electric power steering is exceptionally sophisticated on all models, but on the 460 and 450h Variable Gear Ratio Steering quickens the mechanical ratio (while at the same time reducing effort) at very low speeds, then provides a slower ratio (for more precision) and higher effort at higher speeds.The system matches wheel angle to the speed at which the driver is turning the steering wheel in order to offset any delay in the car's response to steering input.This works especially well on winding roads.A correction feature offsets the effects of crosswinds, making small steering adjustments automatically.

The steering system makes it possible to manage a powerful, rear-wheel-drive car in all kinds of driving and (more important) all kinds of weather.But we felt that both the electric power steering and electric brake system occasionally deliver an unnatural feel through the controls.During ordinary driving, we adapted quickly, but the combination of these electric systems with VDIM proved faintly distracting during enthusiastic driving.In fact, the hybrid GS 450h actually annoyed us because the transition from conventional friction braking to hybrid-style regenerative electrical braking frequently proved clumsy and unpredictable.

Overall, the heavy, 4,134-pound GS 450h is the quickest of the GS sedans, getting to 60 mph in 5.2 seconds, though it's capable of just 131 mph.The 3,945-pound GS 460 launches to 60 mph in 5.4 seconds on the way to a top speed of 149 mph, and the 3,795-pound GS 350 sprints to 60 mph in an impressive 5.7 seconds on its way to a top speed of 143 mph.(The figures for the GS 350 AWD are 5.8 seconds and 130 mph.)

Fuel economy for the GS 450h is rated 22/25 mpg City/Highway on the government's EPA cycle.The GS 460 is rated 17/24 mpg, the GS 350 gets 19/26 and the GS 350 AWD is rated at 18/25.

In our opinion, the GS 350 is more enjoyable to drive than its up-market siblings.The V6 is responsive and just plain fast.The gear changes of the six-speed automatic transmission are virtually undetectable.The GS is not the sort of car that encourages manual shifting, but it is a performance car, and the feeling of acceleration is a large part of its appeal.

More conventional steering and braking help the GS 350 feel more natural than the more-expensive models with all their drive-by-wire technology.The 17-inch wheels provide the best ride quality and the 18-inch tires are available to provide more cornering grip for drivers who feel they need it.In particular, the all-wheel-drive model feels surprisingly alert and maneuverable thanks to its rear-biased power delivery.

The GS 350 gives up some dynamic control at the outer limits of its performance envelope compared to the GS 450h and GS 460, but it's more enjoyable to drive at conventional speed.The all-wheel-drive version of the GS 350 copes with a wide range of weather conditions and doesn't seem to offer many compromises in terms of speed, handling or even fuel economy.

The LS 460 V8 is a paragon of responsiveness, providing ready power from a stop that makes it seem even faster than it is.While the GS 460 is slower in a sprint than the GS 450h, the V8 seems to provide more willing power at midrange and highway speeds.We did find, however, that the eight-speed requires a deep stab of the throttle to coax the downshifts needed for maximum passing punch.

The GS 450h uses the same 3.5-liter V6 as the GS 350, but it is teamed with two electric motors to produce an equivalent 340 horsepower.The GS450h's powertrain is a technological marvel.The gas engine doesn't start until it's needed, and it shuts off at stoplights, so the car can be on and the engine off.The electric motors are capable of powering the car at low speeds.The powertrain is more impressive, though, when you stomp the throttle and find it's faster than Lexus's impressive new V8.The smooth CVT will leave many drivers missing the rewarding climb through the gears of a conventional automatic, but using the manual shift mode with its six preset gear ratios can remedy that.

New Car Test Drive correspondent Kirk Bell contributed to this report from Chicago.