Size matters, particularly when it comes to SUVs and seating capacity. Third seats are the buzzwords in this segment of the truck business, and every manufacturer is hustling to offer one, not because families are so big, but because it adds to the truck's versatility.

The ability to haul seven persons by folding up a couple of extra seats means parents can carry the neighbor kids home from school or take two couples out to dinner. SUVs are all about utility, and if you're going to have a truck, it should be as useful as possible.

In general, carting around three rows of seats requires a big vehicle, but Chevrolet seems to have found a middle ground with the TrailBlazer EXT. Larger than the standard TrailBlazer but smaller than a Suburban, the extended-wheelbase EXT is big enough to be useful yet not quite as tall and cumbersome as some of the larger SUVs. The wheelbase has been stretched from 113 inches to 129, just 1 inch shorter than the Suburban. Overall length, however, is 11.5 inches less than the Suburban. The EXT is roughly 5 inches narrower than the Suburban and about the same height. Think of the EXT as Suburban Lite.

The fact that the TrailBlazer EXT is smaller and more maneuverable than the Suburban is immediately noticeable. It wheels through town almost as easily as the regular TrailBlazer. The only time I felt the drawback of its 129-inch wheelbase was when I turned into parking lot spaces. It does fill up the garage, but not nearly as snugly as its bigger sibling.

Visually, identifying the EXT is easy. You can see the extra length in back doors, which are longer. On the inside, the truck is the same. Front- and rear-seat legroom is essentially identical to the standard model. The third seat is big enough for two full-size adults. Getting back there is easy because the second seat tumbles forward. Folding both the second- and third-row seats forward creates a reasonably flat load floor.

TrailBlazer EXT also provides a cargo shelf with three positions behind the third seat. The shelf is easily accessible when the rear hatch is opened. Grocery bags can be hung from the shelfUs hooks when the shelf is set in a vertical position. The first horizontal position is for a flat load floor, and the second horizontal position can be used to conceal items beneath the shelf. Luggage capacity is diminished considerably with the third seat upright, a situation that doesn't exist with the longer Suburban.

Side airbags are provided for the front seats, and anti-lock, four-wheel disc brakes are standard. Traction control is an option for two-wheel-drive models.

At this time, the 4.2-liter, DOHC six-cylinder is the only engine available. This 270-horsepower, six-cylinder powerplant is smooth and strong. It moves the standard TrailBlazer quite nicely. The extra size and weight of the EXT, however, burdens it just enough that the truck feels a little underpowered and its fuel economy sags. The EPA fuel economy rating is 15 miles per gallon in the city, but in my driving I never got close to that number. Chevy is planning to offer the Vortec 5300 5.3-liter V-8, with greater torque and more than 280 horsepower, as an option in the fall. The V-8 will enhance the EXT's towing capacity and it may well get better gas mileage, to boot.

Chevy's Autotrac system has two-wheel- and four-wheel-drive modes, including a low range. In Auto mode it distributes power to all four wheels as the situation demands, and that is very handy in rain or snowy conditions.

By tacking extra length onto the TrailBlazer to accommodate a third seat, Chevrolet made the EXT handy for buyers who need the occasional use of a third seat but don't want a full-size SUV the rest of the time.

The base price of the four-wheel-drive test vehicle was $33,010. A sunroof, Bose sound system, locking rear differential, off-road tires and metallic paint brought the sticker price to $38,000.

Three years or 36,000 miles.

Point: Adding 16 inches to the TrailBlazer's wheelbase gives seven-seat flexibility in a moderately sized vehicle. It costs less than a full-size Suburban and is more maneuverable.

Counterpoint: The extra size and weight zaps some of the energy from the standard 4.2-liter, six-cylinder engine. Fuel economy suffers, as well. The addition of a V-8 in the fall will be welcome.

Engine: 4.2-liter, 270-hp 6-cyl.
Transmission: automatic Four-wheel drive
Wheelbase: 129 inches
Curb weight: 4,958 lbs.
Base price: $33,010
As driven: $38,000
Mpg rating: 15 city, 20 hwy.
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