As we said, Mercury has made some 500 changes, changes that were already scheduled for the mid-cycle freshening of the Montego, to the new Sable but were pulled ahead in time for the name change.The platform underneath the car is the same, the body and trim are generally the same as the Montego, but almost everything else has changed for the better.

Mercury Sable competes directly against the other large front-drive and all-wheel-drive sedans on the market, including the Toyota Avalon, the Chevrolet Impala, and the Chrysler 300.

The Sable is the largest car in the group, and carries four five-star safety ratings for front, rear, side and rollover crashworthiness.The big kicker in all of this is that, with all the new styling, interior, engine, transmission and standard features upgrades, the price hovers only about $250 above the bland, slow Ford Five Hundred when comparably equipped.

This family of vehicles, including the Ford Taurus sedan and Ford Taurus X crossover, is built on the same platform as the Volvo S80 luxury sedans, with some detail changes to the suspension systems to keep the price in Mercury territory.When all-wheel-drive is ordered for a Sable, it uses the same Swedish Haldex all-wheel-drive system as the Volvo S80 sedans and XC90 crossover SUVs.

The Sable is powered by a new 3.5-liter, 24-valve V6 engine that makes 30 percent more power and 22 percent more torque than the 3.0-liter V6 it replaces.The new 3.5-liter V6 is the same Ford-designed engine that powers the larger and heavier Ford Edge and Lincoln MKX crossovers and MKZ luxury cars.It's paired with a new six-speed automatic transmission built and shared by Ford and GM.

Needless to say, this new engine and transmission combination is much quicker, much quieter and much more responsive than the old Montego powertrain.Mercury says the 0-60 mph acceleration time has been reduced by more than 1.5 seconds, down from 9.2 seconds to only 7.6 seconds, a 17-percent improvement in acceleration performance, which really means something when you're trying to get on or off a freeway or an Interstate Highway.The new engine/transmission combination not only makes more power, it also gets 10 percent better fuel economy, even after adjusting for the new 2008 EPA method now used for fuel economy labeling.

Options include a Convenience package ($475) with a universal remote control, a reverse sensing system, a cargo net, and memory adjustable pedals; a wood package ($195); a DVD entertainment system ($995); AdvanceTrac electronic stability control ($495); moonroof ($895); voice-activated DVD navigation ($1995); 18-inch chrome wheels ($695); engine block heater ($35); Sirius Satellite Radio ($195).The new communications software, the optional ($395) Sync system developed by Ford with Microsoft, is available on all Sable models.

Safety features are complete and include front, side and curtain airbags, ABS, and traction control.AdvanceTrak electronic stability control is optional.With its large physical size and this standard package of safety features, the new Sable has been awarded a Top Safety Pick by the Insurance Institute for Highway Safety (IIHS), and full five-star ratings from the federal government.

Although both cars have multi-pieced brushed-aluminum waterfall grilles, the hoods, grilles, headlamps, bumpers and intakes are completely different on the two cars, and there are differences across the rear panel as well to make the Sable as distinct from the Montego as was possible in a very short turnaround time.The new taillamps have white lenses and LED lighting, the rear quarter panels and decklid have been redone, and the rear bumper has been redesigned with exposed dual exhaust tips.Front to back, there's a bit more bling on the Sable than there was on the Montego, but it's far from overdone.

After you notice the space and the limo-like rear-seat accommodations, you then begin to notice that every piece in the interior, the instruments, controls, shifter, seats, console, and dashboard, has been redesigned, with a more luxurious feel and lots more chrome trim here and there.And they've added a standard MP3 player auxiliary plug inside the center console as standard equipment on all models.

There's more choice for interior schemes with Sable, beyond the basic chrome and aluminum scheme, including faux carbon fiber, guitar maple, and something called San Macassar, all complementing the two-tone interior theme.

Sync offers integration with all Bluetooth-enabled phones and music players, including iPods, via electronic and USB 2.0 connections.Sync can read text messages aloud and features voice recognition for control of both phone and music functions, and phonebook transfer.The system is upgradeable for future players and for additional functions scheduled to arrive in 2009 models.

Our test Sable Limited AWD, with a base price of $29,180 was loaded down with options, including AdvanceTrac electronic stability control, a roof-mounted rear-seat DVD entertainment system, heated front seats, convenience package, wood package, power adjustable pedals, a moonroof, voice-activated touch-screen navigation, Sirius satellite radio, and reverse sensing system, bringing the bottom line to $34,200 and making it the most-loaded Sable it is possible to order.

If you were blindfolded and taken for a ride at full throttle in the new Sable, you'd never believe it's basically the same car as the old Montego.The engine's power, thrust and torque are of a much higher order than the weak old 3.0-liter V6 engine, and the six-speed transmission shifts very quickly with very little time lapse or power loss between gears.It sounds much more powerful without being harsh or intrusive, and it provides some real driving joy when the accelerator pedal is pushed all the way down at the flash of a green light.

The ABS disc brakes were equally powerful, with easy modulation and a very nice, powerful progression at the pedal, and not a lot of dead space at the top of the pedal's travel.Braking starts right at the top and gets progressively better, with electronic brake force distribution to keep the car stable, and full ABS whenever you need it.These brakes are not sports-car large or thick, they just do their job very well for regular passenger car brakes.

The normal front-wheel-drive Sable carries a 3.16:1 final drive ratio for acceleration performance, while the all-wheel-drive version uses a substantially higher ratio of 2.77:1, presumably to keep powertrain noise to a minimum at highway speeds.That was perfectly alright with us, and the car turned out to be a very enjoyable traveling companion in terms of noise, vibration, harshness, and powertrain intrusion.

With traction control and optional AdvanceTrac stability control, the computers take over whenever there's a negative encounter with rain, snow, ice or mud, to keep the car going in its original, intended direction, flat and stable, and we count that well worth the additional $1850 for the AWD system.

The new electric power steering system is overboosted at parking and low road speeds to suit the tastes of most American customers who like effortless steering, but it is also accurate, with good feedback, and is not overly assisted in high-speed or highway driving.The new Sable's ride is soft and compliant, with 10 percent more suspension travel built in, with some body roll in the fast corners, and it has a noticeable upward pitch of the front end on hard acceleration, but most of the time, the 2008 Sable is a very pleasant car to be in.

We found the Sable to be very quiet and smooth on the open road, with excellent outward vision in all directions because of all that tall glass, with a nice, high seating position, very comfortable and supportive front bucket seats, and instruments and controls that were easy to look at and easy to use.

The navigation system was easy to learn and use.The gray graphics of the system don't match the blue-green graphics on the rest of the instruments, however.

Jim McCraw filed this report to NewCarTestDrive.com from his base in Dearborn, Michigan.