Mercury is Ford's Buick - the "step up" brand from Joe Sixpack Ford, but not quite Lincoln, either. Like Buick, the Mercury brand was conceived many decades ago, when American automakers dominated the market and there was no such thing a Japanese luxury brand.

It made sense in those days to have mid-range/almost-luxury brands like Buick and Mercury; they were the cars of the American upper middle classes - white collar, professional types who wanted something nice - but not overly flashy.

Today, a brand like Mercury is a harder sell - in part because "Joe Sixpack" Fords are no longer especially plebian. Many can be larded up with features and equipment that render them the functional equivalent of entry-level luxury (or outright luxury) brands. The supposedly higher-end brand (Mercury) loses some of its former exclusivity when things like leather seats, climate control air conditioning, GPS and DVD navigation systems become commonplace on supposedly "working man" Fords - and when several of those "working man" Fords carry MSRPs well over $40,000.

Two, Mercury no longer has any genuinely unique vehicles not also sold as Fords. That makes it doubly hard to create a "Mercury identity" - and justify the higher-than-Ford prices.

Consider the '08 Mariner.

This compact SUV is basically a Ford Escape in dinner clothes. The two have identical drivetrains, the same basic chassis and suspension systems, overall dimensions, etc.

How to push them apart?

The Mercury version of Ford's compact SUV does offer some unique design touches and equipment - including softer fonts for the instrument cluster facings, "cool blue" lighting, pewter/stainless steel trim to accent the dash and center console, a chrome shifter plate and door handle pulls plus attractive two-tone leather/Alcantara suede inserts for the seats and door panels in top-of-the-line Premier models.

It's a similar story on the outside. While the overall exterior shape and physical dimensions of the Mariner are virtually identical to the Escape, the use of monochromatic (all one color) paint schemes, clear tail-light lenses and pewter/stainless trim styling touches - including tail-light guards and a very dignified-looking vertical slat grille with offsetting fog lights recessed into the lower section of the bumper - help class up the joint considerably.

The Escape still looks like a two-thirds-scale Explorer - even when it's loaded up with GPS and leather seats. As Seinfeld would say, not that there's anything wrong with that. Nonethelesss, the Escape does come across as more truck-like and working class while the Mariner has the more refined and uptown look of a college grad - and white collar work.

Under the hood, though, everything's identical.

Like the Escape, the Mariner comes, with the buyer's choice of either a 2.3 liter, 153-hp four-cylinder engine, a 3 liter V-6 rated at 200 hp or a hybrid gas-electric powertrain. Front-wheel-drive is standard - with an all-wheel-drive system available optionally.

One notable difference between the two is the Escape still offers the option of a manual transmission - at least, with the four-cylinder. With the Mariner, both engines come with four-speed automatics only.

And here we come to a weakness shared equally by both: They're underpowered, overweight - and thus, slow. An Escape/Mariner may be a "compact" SUV - but its 4,500 pound curb weight is a lot to ask a four-cylinder engine to drag around. Arguably, too much to ask. Even the optional V-6 has trouble getting this vehicle to 60 mph in 10 seconds flat. The four-cylinder's simply overwhelmed. Its 153 horsepower is in the same ballpark as the power you'd find in a compact car that weighs 1,500 pounds less. It's like asking grandma to carry you up the stairs. She may be able to do it, but the effort will be obvious.

And painful.

For comparison, the Honda CR-V only weighs about 3,400 pounds; the Toyota RAV-4 comes in at an even more svelte 3,300. That is a huge difference - and one you'll be reminded of every time you try to climb a grade with a full load of passengers - or pull out to pass a dawdling semi.

It's a shame that Ford decided not to update the Escape/Mariner's drivetrain for 2008. Virtually everything else got tweaked - from the exterior cosmetics to the revised interior (which in Mariner includes a driver information display at the top of the center stack, plus an acoustically laminated windshield and thicker carpeting to keep outside noises outside). A more modern five or (better yet) six-speed automatic would have made a big difference. But a vehicle that weighs this much needs at least 170 horsepower from its base engine - and 220 or so from its optional engine.

The Escape/Mariner's asthmatic acceleration is without question its weakest point. It's not dangerously slow - but it is noticeably slower than all of its newer, more up-to-date competitors.

One way to crutch things a bit is by skipping the optional AWD system. Front-drive versions have to carry less weight (and there's less inertial load) so they feel a bit more frisky, especially when loaded up with passengers.

AWD can be a nice feature to have - but you may not really need it. It depends on where you live and how often you have to drive in snow (or on unpaved/muddy roads). Front-wheel-drive is often more than enough, most of the time - and maybe all of the time if you live in an area with a mild climate and rarely, if ever, venture off paved roads. If you don't need it, don't buy. Your Mariner will be a little quicker, drink a bit less fuel - and cost less, too.

Complaints about power/acceleration aside, the Mariner (like the Escape) is roomy on the inside, handles nicely and is pleasant to drive. Nice features include a two-piece rear liftgate that lets you open just the glass section - or the entire thing. Being able to close the gate but keep rear glass open can be handy when you need an extra couple of inches to cart some unwieldy object home. If you've got a dog, he'll like it, too.

In addition to its very stable car-like ride and handling, the Mariner bolsters its occupant protection credentials with newly standard (for 2008) front seat side-impact air bags, standard full-row head/curtain air bags, electronic stability control to reduce the chances of a rollover, ABS brakes and a tire pressure monitor.

Base FWD Mariners ($20,730) come with the power windows, locks, remote keyless entry, air conditioning, stereo with CD and MP3 player and 16x7 alloy rims. Premier versions add climate control. AWD runs the tab up to $22,480.

The V-6 is basically a stand-alone option, offered with either FWD ($21,730) or AWD ($23,480).

Top-of-the-line Premiere models are V-6 only but you can choose FWD ($23,630) or AWD ($25,380). These Mariners also upgrade to the snazzy-looking Acantara suede seat inserts (with power driver's seat), dual-zone climate control AC, upgraded audio system and Park Assist sensors. GPS, a sunroof and 320 watt premium audio system are among the Mariner's big ticket options.

V-6 models call pull up to 3,500 pounds. That's more than twice the max-rated tow capacity of the Honda CRV (1,500 pounds), which only comes with a four-cylinder. This is one category of functionality where the Mariner has an objective advantage over Honda's compact SUV. The Toyota RAV-4, meanwhile, may offer a great deal more power (and better acceleration) when equipped with its optional 269 horsepower 3.5 liter V-6, the but max tow rating is exactly even with the Merc's at 3,500 pounds.

A factory-installed hitch package is available and includes a 4-pin connector, wiring harness and Class II receiver.

The bottom line is that while both the Escape and the Mariner are getting a bit long in the tooth - and are a little on the slow side - they're still surprisingly appealing overall.

And the Mercury version offers a bit more panache for not much more money - as well as some unique touches you still can't get in the Ford doppelganger.

It may not be a lot.

But it might be just enough.