For 2003, the TrailBlazer adds an extended-wheelbase model with seating for seven, and an optional all-aluminum V8 for more towing power. The fuel tank is larger. And there's even a new North Face Edition with exclusive interior and exterior trim.

The V8 delivers strong torque for towing, but the six-cylinder engine delivers plenty of power for the TrailBlazer. The long-wheelbase TrailBlazer EXT sacrifices handling for third-row seating.

At the rear, there's a convenient and practical step in the center of the rear bumper, sort of a big functional notch. But the twin round taillights stacked over the backup light at each corner are kind of lumpy and googly eyed.

Overall, TrailBlazer looks sturdy and neat, with confident lines that express utility. The pillars and window lines are graceful, while the headlamps and turn signals (split by the grille crossbar) are stylish. Big fender flares visually express the vehicle's boldness, and may be either body color or silver.

Still, the most dramatic feature of the TrailBlazer may be what's under its hood: not a V6, but an all-aluminum, double-overhead-cam, 24-valve engine with variable valve timing and six cylinders lined up straight in a row.

Inline sixes were once the industry norm. An old reliable straight six served as the base-level power plant in Chevrolet trucks (and passenger cars) from 1929 right into the mid-1980s. Jeep still runs a straight six in the Cherokee. BMW and Lexus build some of the most sophisticated sixes in the world, and both companies prefer an inline configuration. An inline six is inherently smoother than most V6s, and simpler as well; whereas a V6 takes up less space, and a 90 degree V6 can be manufactured using V8 tooling, two reasons for the soaring popularity of V6 engines in the 1980s and 90s. Now, however, thanks to advancements in electronics, metallurgy and manufacturing, the straight six is poised for a comeback.

The TrailBlazer's Vortec 4200 is no ordinary straight six. From 4.2 liters, it produces a stunning 275 horsepower, 35 more than Ford Explorer's optional 4.6-liter overhead-cam V8. And it has a very broad torque curve, peaking at 275 pounds-feet, only 7 pounds-feet less than the Ford V8, and 400 rpm sooner. The Vortec also features electronic throttle control, an electrical system using silicon circuit boards (replacing some 1100 feet of copper wire), coil-on-plug ignition (thus no plug wires), and a seven-quart oil pan with a clever tunnel for the front drive axle, which allows the longish block to be mounted six inches lower, contributing to better balance and a lower center of gravity.

Because the engine is so quiet and smooth at idle, a feature called "intellistart" was added which prevents the starter from grinding if the key is turned when the engine is already running. With a mixture of amusement and pride, GM engineers report that this happened to them all the time during development.

Attention to detail in other places is evident, from a battery box that draws in cooling air, to remarkably sanitary wiring under the hood, to rear-seat headrests that conveniently flip down for better rearward driver visibility.

The TrailBlazer's Autotrac system, standard on 4WD models, features four settings: 2WD, Auto4WD, 4HI and 4LO. In Auto, which shifts power to all four wheels as conditions require, the TrailBlazer can be towed without having to disconnect the driveshaft, a very convenient feature. Switching in and out of 4WD can be done on the fly with a flip of the switch, although the transmission must be in neutral to engage or disengage 4LO.

The chassis and suspension are also highly developed, featuring a list of sports car stuff: rack-and-pinion steering, beefy four-wheel vented discs with twin-piston calipers in front, independent front suspension with short/long control arms, solid rear axle using five-link location with Bilstein gas-charged shock absorbers and coil springs, thick antiroll bars front and rear. It was the first truck for the TrailBlazer's chief designer, Ted Robertson, who brought a resume to the assignment that includes the '90s Camaro/Firebird. GM wanted his soul as well as his experience in their midsize SUVs, and they got it. His approach was to put some "sport" in Sport Utility.

The standard-wheelbase TrailBlazer is 8.3 inches longer and 6.9 inches wider than the old Chevy Blazer. The track (the distance between the left and right tires) is the widest in the class, 2.2 inches wider than the Explorer in front and 0.9 inches wider in rear. Still, the TrailBlazer has a very tight turning circle of 36.4 feet, because the suspension and engine design allow for large steering angles.

Finally, the chassis rails are shaped by hydroforming, a process pioneered in the '97 C5 Corvette; it makes the rails stronger and lighter. No less than eight crossmembers contribute to a claimed 260 percent increase in torsional rigidity, and there are 12 tuned body mounts made of urethane.

Still, if you look at interior dimensions for the two vehicles, you might wonder where those extra 16 inches went. Head, hip, and leg room in the Explorer's third row measure 39.0, 45.3, and 34.8 inches, respectively. The corresponding numbers for the TrailBlazer EXT are 38.5, 45.9, and 32.2. TrailBlazer is 2.6 inches wider than Explorer, which accounts for the additional hip room. But clearly, the Explorer's independent rear suspension, and resulting low floor, allowed Ford to pack more leg and head room into a significantly shorter wheelbase.

On the other hand, the long-wheelbase TrailBlazer does offer significantly better second-row leg and hip room than the Explorer, with 37.5 and 58.4 inches, respectively, versus the Ford's 35.9 and 54.2 inches. Even the standard-wheelbase TrailBlazer betters the Explorer in the second row, with 37.1 inches of leg room and 58.1 inches of hip room.

TrailBlazer seats come in two grades of fabric (LS and LT) or rich-feeling leather (LTZ). The adjustment is manual in LS and gains in trickery all the way up to eight-way power operation with memory (including outside mirror adjustment) and optional heating on the LTZ. Chevrolet says the front buckets are designed to accommodate heights ranging from 4 feet 10 inches to 6 feet 2 inches, but there is a noticeable lack of side bolstering. The front seats don't do justice to the TrailBlazer's ride, allowing the occupants to feel a side-to-side jouncing that doesn't exist in the similar GMC Envoy, which shares the same chassis and suspension but has better seats.

Interior lights abound, including reading lights. GM calls the interior lighting "world class." It was developed by the Rensselaer Polytechnic Institute Lighting Research Center in Indiana.

The instrumentation is complete and clean. A big tachometer is on the left, speedometer in center, and on the right are smaller gauges for water, battery, gas and oil. Brushed nickel is the basic trim, while wood comes with the leather interior. The four-spoke leather-wrapped steering wheel (standard on LTZ) has eight buttons, for climate, sound, cruise control and a driver information center in eight languages.

The console includes an open storage bin, an enclosed compartment and two cupholders forward of the gear lever (plus two more for the rear passengers). There are pockets in the front doors and behind the front seats, though none in the rear doors. Standard behind the rear seat is a small hidden compartment under the floor, while optional features include a cargo net, scrolling tonneau cover and power outlet.

The overhead console (standard on LTZ) includes a sunglasses holder, plus Travelnote digital recorder. Heating and air conditioning can be controlled separately by the driver, front and rear passengers.

Depending on trim level and options, the sound systems include radio/CD, radio/CD/cassette, six-disc in-dash CD, or six-speaker 275-watt Bose system. We found the Bose system offered outstanding sound quality and adjustment versatility. All the systems include RDS (Radio Data Systems) technology, allowing the listener to search for stations by type, display information including song and artist information, and provide traffic and weather updates. Rear seat controls and headphone jacks are standard with LTZ, optional with LT and unavailable with LS.

The OnStar communications system is standard with LT and LTZ, optional with LS. It includes GPS navigation, hands-free cellphone communication and a free first year of safety and security service (automatic crash and theft reporting, as well as remote unlocking if you lock yourself out). Mind-boggling possibilities include everything from having your email read to you by a computerized voice (Virtual Advisor) to getting directions to the nearest ATM.

Also available is a rear seat DVD entertainment system, with a seven-inch flip-down screen and wireless headphones.

The inline-6 engine feels more powerful than a V6 with the torque of a small overhead-cam V8. It's so smooth that it doesn't sound like much of anything. And the faster it goes, the smoother it gets. With an official Mexican Highway Patrol escort along on the test drive, we felt free to briefly run the TrailBlazer up to 100 mph, and it was above 80 where the inline engine really showed the silky side of its character.

It showed the beefy side down low. Our LTZ test model was equipped with the optional 4.10 rear differential, and was able to blast past Mexican trucks on steep uphill two-lanes with calm confidence. It surges with acceleration performance without a downshift, as the ample low-end torque doesn't need it, and therefore the four-speed automatic transmission isn't programmed for it. Ninety percent of the peak 275 pound-feet of torque is available at 1600 rpm, and it's still there at 5600 rpm. The full-throttle upshift comes at 6000 rpm, and the engine is still only striding, not screaming.

The smooth-shifting transmission is the proven Hydra-Matic 4L60-E, used in GM applications from Corvettes to Cadillac Escalades.

Towing was a high priority with the TrailBlazer. Six-cylinder models are rated at 6300 pounds with 2WD, 6200 with 4WD. The six-cylinder engine is designed to run cool (thanks in part to that big seven-quart oil pan) and efficient.

Big ventilated disc brakes provide stopping power and four-wheel ABS is standard. Under hard braking, the nose didn't dive, keeping the TrailBlazer remarkably level and stable.

We found the ride excellent, very smooth: in a word, carlike, without being too soft. TrailBlazer was designed to roll (lean) exactly five degrees in the corners, and then stop leaning. The track is the widest in the class, 2.2 inches wider than the Explorer in front and 0.9 inch wider in rear. This, coupled with the lowered engine position, drops the center of gravity. A vehicle with a low center of gravity is generally less likely to roll over than a vehicle with a high sense of gravity.

The Chevy TrailBlazer is designed to be driven off road. We found the TrailBlazer impressively stable on washboard surfaces. It bottomed on dips, however, signaling that the optional skid plates are necessary for off-road driving. Our test model (equipped with 17-inch BFG Rugged Trail radials) had the skid plates, of course, which we dragged in soft sand, chugging easily along at 5 mph in Auto4WD.

As impressed as we were with the TrailBlazer, we've been less impressed with the TrailBlazer EXT. The long-wheelbase EXT lacks the responsiveness and stable handling of the standard TrailBlazer. EXT feels long and narrow. That's not surprising, given that EXT is longer, narrower and taller than the Chevy Tahoe. TrailBlazer EXT's wheelbase is stretched dramatically, by 16 inches. It's suspension is soft. It wallows in corners. On exit ramps, when braking and turning at the same time, it does not feel as stable as a TrailBlazer or Tahoe. On the highway, the EXT wanders around in the lane. Stability is also affected by strong crosswinds at high speeds. Even equipped with the optional V8 engine, the TrailBlazer EXT feels distinctly underpowered. It weighs nearly 300 pounds more than the standard TrailBlazer.

The base engine for all Trailblazers is the Vortec 4200, which was all-new for 2002. This sophisticated 4.2-liter inline-6 uses dual overhead camshafts, four valves per cylinder, and variable phasing for the exhaust cam to produce a stunning 275 horsepower, best in a class that includes Ford and Jeep V8s. Its torque output is impressive as well, at 275 pounds-feet.

For 2003, extended-wheelbase Trailblazers are available with an optional 5.3-liter, overhead-valve V8, developing 290 horsepower and 325 pounds-feet of torque. Equipped with the V8, a two-wheel-drive Trailblazer EXT can tow 7,200 pounds (or 7,000 pounds with 4WD).

Standard equipment on all models includes dual-stage driver and passenger airbags, which inflate with less intensity in slower crashes. Seat-mounted side-impact airbags are optional ($350).

LS ($27,595) is nicely equipped with dual-zone air conditioning, CD player, reclining bucket seats and floor console, power windows and programmable door locks, tilt steering, four-wheel-disc brakes with ABS, 16-inch aluminum wheels, perimeter lighting, and three power outlets. LS is available only on the short wheelbase.

LT ($29,725) adds cruise control, fog lamps, a Homelink transmitter, driver information center, luggage rack, heated power mirrors, leather-wrapped steering wheel, premium-grade upholstery with eight-way power for the driver's seat, and an alarm. LT also comes with GM's OnStar security system with GPS tracking and cell phone communication, including emergency assistance and remote unlocking.

LTZ ($33,570) is the luxury-grade TrailBlazer, with leather upholstery, dual power seats (and memory for the driver), automatic climate control, overhead console, and audio controls in the rear seat and on the steering wheel. Wheels and tires upgrade from 245/70R16 to 245/65R17.

The North Face Edition ($35,615) is essentially an LTZ with unique North Face seats, mesh map pockets, Rainsense automatic wipers, liftgate lighting, an under-floor storage cargo liner, heavy-duty floor/cargo mats, an adjustable cargo shelf with a table (EXT model only) and North Face duffel bags and blanket. It also sports some unique exterior identification.

The LT and North Face Edition are offered in extended-wheelbase form. The LT EXT ($31,645) and the North Face EXT ($36,955) come with third-row seating with separate rear-seat heating and air conditioning controls. They are fitted with 17-inch wheels and tires.

Four-wheel drive (4WD) adds $1775-$2355 to all of the prices above, depending on trim level. (It costs more on the more premium models.) Skid plates for the transfer case and fuel tank ($130) and a locking rear differential ($270) are optional on all four models (and mandatory on North Face Editions).

The LS comes with a trailer hitch platform; LT and LTZ add a wiring connector for trailer brakes. The standard final drive ratio on all TrailBlazers is 3.42:1; however 3.73 and 4.10 ratios are available ($50) for more responsive towing. (The 4.10 ratio is not available with the V8 engine.)

Options for the LT and LTZ include 2WD traction control ($195), running boards ($375), a Bose sound system ($495), and a rear-seat DVD entertainment center ($1000). A sliding electric sunroof costs $550 on LT and LTZ, but is available on LS only as a package with OnStar for $800.

TrailBlazer sports a nice design and a well-executed interior, though GM's seats could use some improvement.