The 2010 Nissan Xterra comes in four models.Most offer a choice of rear-wheel drive or four-wheel drive.All are powered by Nissan's award-winning aluminum V6, stroked to 4.0 liters and making 261 horsepower and 281 pound-feet of torque at 4000 rpm.With 4WD and the smooth (optional) five-speed automatic transmission, the Xterra achieves 15 city and 20 highway miles per gallon, a bit more with 2WD or the standard six-speed manual transmission.

An Off-Road model is available that will go pretty much anywhere.It comes with Hill Descent Control, heavy duty trail tires, and skid plates.The electronic 4WD system is part time, with three functions available: 2WD, 4WD High and 4WD Low.

Last year (2009) Nissan freshened the Xterra's appearance a bit and, more importantly, made front-seat side-impact and full-length side-curtain airbags standard on all models.The Xterra now rates four of five stars in NHTSA crash tests for frontal impact, and three stars for rollover.For 2010, Nissan has made last year's Gear Package standard on S and SE models, and what was the Technology Package is now standard on SE and Off Road.

The Xterra S 2WD ($25,420) and 4WD ($27,470) come with the automatic transmission only, and add an eight-way adjustable driver's seat, power mirrors, an interior microfilter, fog lamps, aluminum step rails, roof rack crossbars and gear basket, and alloy wheels with BFG Long Trail tires.The X-model's cargo-area carpeting is replaced by an easy-to-clean plastic cargo floor with two C-channels and four moveable hooks to strap down mountain bikes and things, plus additional hooks in the ceiling and side panels.

The Terri SE 2WD ($28,350) and 4WD ($30,400) upgrade further with leather seats; leather-wrapped steering wheel with Bluetooth and audio controls; Rockford Fosgate audio with 6CD changer, MP3 capability, auxiliary input, and XM Satellite Radio; auto-dimming inside mirror with compass; illuminated vanity mirrors; first aid kit; cargo net; and 17-inch alloy wheels.Mirrors and door handles are body color instead of black.

The Xterra Off-Road comes only with 4WD, but with a choice of manual ($29,200) or automatic ($30,400) transmission.Equipment is similar to SE, except that the Off-Road skips the step rails and leather seats.(It features its own unique red-and-gray rugged fabric upholstery.) Off Road adds roof-mounted driving lights, a front passenger seat that folds flat, an electronic locking rear differential, Bilstein gas shocks, and skid plates for the oil pan, fuel tank and transfer case.The automatic transmission version comes with Hill Descent Control and Hill Start Assist as well.Either way, Off Road rolls on BFG Rugged Trail tires mounted to 6-spoke 16-inch alloy wheels.

Splash guards ($135) for the X are the only factory option, but port-installed accessories range from a tow hitch ($460) to a dockable DVD player ($495) and Garmin portable navigation.But not all accessories are available on all models, so check with your dealer for details.

Safety equipment on all 2010 Xterra models includes dual-stage front airbags, side-impact airbags in front, roof-mounted airbag curtains with a rollover sensor, and the LATCH system (Lower Anchors and Tethers for CHildren).Vehicle Dynamic Control and vented disc brakes with ABS and EBD also come standard, along with the government-mandated tire pressure monitor.

This year's remaining color choices are Silver Lightning, Night Armor, Super Black, Navy Blue and Avalanche.You get the idea.

The front end is all very symmetrical and beef.Tidy, no-nonsense headlamps.The lower corners of the front fascia are rugged and massive, although not conspicuously so because they're flat black.The grille is sort of a black egg-crate hole with a floating chrome Planet Nissan logo in the center, surrounded by an inverted isosceles trapezoid (finished in a flat silver plastic Nissan calls Sandblast Aluminum) with wings that look like handles on a loving cup trophy.More Sandblast Aluminum trim wraps up from underneath like a bib, suggesting the skid plate that's real only on the Off Road model.

Our test vehicle was an Off Road, which meant the moldings on the doors were flat black instead of body color, which is kind of ugly especially since there are exposed bolts underneath, apparently where the running boards attach to other models.

Boxy fender flares hang over the wheels: decidedly common six-slot units on the X, and no-more-interesting five and eight-spoke cast-alloy patterns on the S and SE, respectively.At least the dark centers and six machine-finished spokes of the Off-Road's wheels add some interest.Maybe it's just as well, because snazzy wheels might not go with the mud flaps.

The Xterra's distinction comes as much from its roof rack as any vehicle on the road.It was tweaked last year, although how much tweaking can you do to a roof rack? Nissan calls its sloping front surface an air dam, and that's where the Off Road model houses its 50,000-candlepower roof lights.All but X have a 'gear basket' right behind the air dam that's meant to hold wetsuits and ski boots and muddy mountain-biking clothes; it's covered by a lid held down with a sloppy plastic latch.

The back half of the Xterra is the part that people mostly notice.The brick has big windows.What's that lump on the tailgate? They might ask.That's where the First Aid kit goes.That kind of thing is what the Xterra has been all about, successfully, ever since it was introduced.And other things, such as the side steps that make it easy to climb up on the bumper and reach the roof rack.

The driver and front passenger seat recline way back, although when we tried to take a nap at a rest stop we couldn't line up our butt, the gap between the seat and seatback, the small of our back, the back of our head, and the headrest.The reclined seats might better fit six-footers.

The center console is deep, with coin holders and two cupholders and the emergency brake handle.Nice tray forward of the shift lever, glovebox of decent size, steering-wheel controls on most models.Good visibility out the rear liftgate window and big side rear windows.

The rear seat, split 60/40, folds flat with a few steps.Some SUV seats fold easier, some with more difficulty.Good grab handles over the rear doors, one map pocket on the driver's seatback, two 20-ounce bottle holders.Legroom in the rear seat is a bit lacking, at a mere 34.4 inches, although a person can fit their knees in there, even behind the driver with his or her seat slid back.

The cargo area is where the Xterra comes into its own.All but the base model have an Easy Clean surface, like hard vinyl, making your wet dog no problem.There's a nice deep hidden compartment under the floor, and no less than 10 utility hooks on the floor, sides and ceiling.Space and nets to carry jugs.We were intrigued by the adjustable track system in the cargo floor, similar in design to the Utili-track system offered on the Nissan Titan and Frontier pickups.Like the Easy Clean surface, it's standard on all but the base-level X.

During our week in the Xterra, including 40 miles on gravel and dirt roads, we didn't encounter any harsh spots in the ride, which is saying a lot, although the side-to-side motion is a bit more pronounced than with crossovers.

We took a few runs on a rough off-road course, and the Xterra met every traction and crevice challenge it faced, using 4WD HI and 4WD LO, easily switchable with one knob on the dash.Also, with short overhangs front and rear, things don't easily drag in the gulleys.You can take it hunting or dirt biking to the top of rugged mountains with no worries.

We tested Hill Descent Control on the off-road course as well.Provided only on Xterra Off Road with automatic transmission, Hill Descent Control (HDC) allows you to travel down a steep hill and rely on electronics (raising both feet off the pedals) to keep the Xterra safe and steady at 5 mph, with throttle control and ABS applied by the truck's tiny brain and feet, better in this circumstance than your own big ones.If you live in a place that has snowy and icy hills in winter, HDC, available on some other SUVs (that don't have to be off-road equipped), could save your life or the life of another, for example a passenger on the sidewalk.It also helps the driver keep the rear from sliding out on a steep, muddy descent, so you don't slowly slide off the trail and into a tree.

Hill Start Assist also comes only on the Xterra Off-Road with automatic transmission, though that seems strangely misplaced.Hill Start Assist allows you to start moving forward on a steep uphill, without drifting back, useful off road and in San Francisco.But with an automatic transmission, that's not a problem, because you have two feet and there are only two pedals.It's needed with the manual transmission Xterra, if anything, but Nissan didn't design HSA to work on that one.

The 4.0-liter V6 that's used in the Xterra is a great engine, a stroked version of the award-winning 3.5-liter that's used in the 350Z sports car and other Nissans.It has all the right stuff: aluminum block and heads, Teflon-coated pistons, Continuous Valve Timing Control (CVTCS), Nissan variable Induction Control System (NICS), silent timing chain and microfinished camshaft and crankshaft surfaces, digital knock control system, and 105,000-mile spark plugs.

Fuel economy for the Xterra is an EPA-estimated 15 city and 20 highway miles per gallon with 4WD, a bit more with 2WD.It would get more, if the body wasn't such a brick.

The engine certainly has plenty of horsepower and torque, 261 hp and 281 pound-feet, but its torque curve, peaking at a high 4000 rpm, is more suited to a sports car than a truck.As a result, the automatic transmission kicks down a lot at casual speeds, even 35 mph, from fifth gear to fourth; but because it's so smooth, you hardly notice it.However you do notice that the Xterra doesn't feel terribly powerful.Until you boot it, and then it blows you away.When you let it run, you find yourself driving a truck SUV that wants to be a Nissan 350Z.There will be no problem passing on two-lanes, or running with the hot sedans up long freeway slopes.

NewCarTestDrive.com correspondent Sam Moses reported from California.