The Mercury Grand Marquis is so old... "How old is it?" It's so old, its platform debuted when Jimmy Carter was president. It's so old, a cassette deck is an optional extra. It's so old, the Grand Marquis and its relatives are the only cars still built using body-on-frame construction. It's so old, Ed McMahon will soon respond, "Yessir, that's old."

So the Grand Marquis is advancing in years, but some oldies are goodies, right? Well, its old-school approach does have a few benefits, like its robust simplicity and cheap maintenance costs (which have made it and its Crown Victoria twin a favorite among the nation's livery and law-enforcement communities). But there's a reason cars are no longer built like this big old Mercury -- actually, there are quite a few reasons. Thanks to the marvels of modern vehicle design, Ford's newer full-size sedans manage to offer as much interior room while taking up less real estate on the road. And by virtue of more sophisticated engineering, all offer a vastly superior driving experience with better handling and body control.

For those who are not commercial-fleet buyers, the 2009 Mercury Grand Marquis' main selling points are its wide-body interior space, rock-solid safety scores and low price. Anyone who has ever taken a ride in a Grand Marquis or Crown Vic taxicab (or perhaps less fortunately, police cruiser) knows how large the interior is. Hiproom and shoulder room are particularly impressive. You should also have noticed that the trunk is only slightly smaller than a Smart car.

But let's compare the Grand Marquis to Mercury's other, thoroughly modern, full-size sedan: the Mercury Sable. This Taurus clone's trunk is actually a tad larger than the Grand Marquis' trunk; its rear-seat head- and legroom are more generous; and its crash test scores are identical. Plus the Sable hits the registers for about the same price and has a similarly powerful, but more fuel-efficient, V6 engine. It also has a much nicer interior, a wider array of available features and is much easier and less cumbersome to drive. We could go on.

The 2009 Mercury Grand Marquis' longtime sibling, the Ford Crown Victoria, is now sold only to fleet buyers, meaning folks who still want a throwback rear-drive large sedan must stick with the Mercury or throw down a few more bucks for the related Lincoln Town Car. But we urge you to not still want such a throwback rear-drive large sedan. Other full-size sedans, like the Sable and Taurus, should better meet or exceed your car-buying needs, while others, like the Chrysler 300, Hyundai Azera and Toyota Avalon, are also worth considering.

The 2009 Mercury Grand Marquis is a full-size sedan in one trim level known as LS. Standard equipment includes 17-inch alloy wheels, rear air suspension, keyless entry and exterior keypad entry, auto on/off headlamps, foglamps, cruise control, full power accessories, automatic climate control, an auto-dimming rearview mirror, a power 40/20/40-split front bench seat, leather upholstery, a leather-wrapped steering wheel and a CD player.

Options include chrome-clad wheels, heated front seats, a leather/wood steering wheel with audio and climate controls, power-adjustable pedals and a "dual media" stereo with a cassette and CD player.

The rear-wheel-drive 2009 Grand Marquis is powered by a 4.6-liter V8 coupled to a four-speed automatic transmission. Output is 224 horsepower and 275 pound-feet of torque. Fuel economy is 15 mpg city/23 mpg highway and 18 mpg combined, notably less than other large sedans.

Standard safety equipment includes antilock disc brakes, traction control and front-seat side airbags. Stability control and side curtain airbags are not offered.

Despite missing a few safety features, the Grand Marquis nevertheless has scored well in tests by the National Highway Traffic Safety Administration. It rates a perfect five stars in frontal-impact crash protection, and when equipped with side airbags, it earns five stars for front and rear side-impact safety as well. The big Mercury sedan also earned the top rating of "Good" in frontal-offset crash testing conducted by the Insurance Institute for Highway Safety.

Like the interior, driving the 2009 Mercury Grand Marquis is none too different from piloting one from 15 years ago...or even 15 years before that. Due to the vehicle's size, pillow-like suspension and low-effort steering, it has all the road feel of a pontoon boat. These may seem like positives to some folks, but quite simply, newer full-size sedans are easier to maneuver and better to drive, while still offering safe structures and comfortable rides. On the upside, the standard V8 provides plenty of acceleration for most driving situations.

The Grand Marquis has a wide, spacious interior that can seat up to six in a pinch. Nevertheless, the rear seat is matched or surpassed in roominess by newer, better-driving full-size sedans. Controls and instruments are simple and easy to decipher, but the overall design is dated and some controls are difficult to reach. If you've taken a cab to the airport in the last 15 years, you already know the trunk is huge, with 20.6 cubic feet of space capable of swallowing copious amounts of luggage or several sets of golf clubs.