For the most power you need a Denali and its 6.2-liter V8: 403 hp and 417 lb-ft of torque.This powerhouse gets the Denali moving with ease, delivering very similar power-to-weight as the Sequoia.The Denali's tow rating is 100 to 300 pounds less than other Yukons and it is not available with a 4WD system that has low-range gearing.

Both V-8s have a system to shut off half the cylinders when not needed, a condition that exists under power infrequently in big trucks.Yukon EPA ratings typically run 14 city/19-20 highway with the XFE 2WD version rating 15/21, in the same neighborhood as the Expedition.The considerably more powerful Denali is in the 12-13/18-20 range, much like the similarly powered Toyota Sequoia and Infiniti QX56.Recent EPA ratings are less optimistic than they used to be, but any way you look at it, you're going to use lots of gas.

The Hybrid Yukon offers big gains in city fuel economy, netting EPA numbers of 21/22 for 2- or 4-wheel drive.Real-world drives show EPA numbers for hybrids remain on the optimistic side.In back-to-back drives between hybrid and standard GM SUV's we found the standard (lighter) truck just edged the hybrid on highway fuel economy while the hybrid was better in urban environs, getting around 17 mpg versus the 5.3 around 13 mpg.EPA diesel numbers on the other hand skew pessimistic, with Mercedes' GL and ML350 VW's Touareg, Audi’s Q7 and BMW X5 diesel all in the 17-19/23-26 range and easily matched.

The numbers game continues with tow ratings.Yukon ratings aren't quite as high as Expedition and Armada, and 1500 pounds below the Sequoia's top 10,000-pound rating.To find real towing ability you need to know the trucks' GCWR and subtract the truck (and all passengers/cargo) from it.For example, a Yukon rated to tow 8200 pounds max might pull only 6700 pounds with the truck loaded; VW's Touareg diesel is rated at 7716 pounds, but that is with the vehicle loaded.

Driving a Yukon is pleasant.Power comes on smoothly, with no surges or hiccups, and it is accompanied by a pleasant tone that reminds us of classic dual exhaust.Transitions effected by the fuel-management system are invisible, with the only indication a telltale in the information display in the tachometer.The six-speed automatic sorts out gears well.It has a manual shift function managed by a rocker switch in the handgrip on the column shift lever that rev-matches downshifts, but unlike most competitors you must first move the lever to M.

The Hybrid works seamlessly and doesn't require any new driver action, just some familiarity with the different noise and, for maximum efficiency, driving style.At very low speeds propulsion is by electric power only, and you have to watch for people walking out in front of you in parking lots since there is only tire noise and some whirring when you start or stop.The system will do 30 mph on electric alone in ideal circumstances but in most cases the gas engine is on by 10 mph.It usually shuts off the gas engine when the vehicle is stationary and the majority of time your foot is on the gas pedal it is a combination of the gas engine and electric motors powering you.

If you step on the gas hard as you might to get across a busy street there is a moment, some fraction of a second, before the gas engine starts and the system delivers its full 367 lb-ft of torque, so you should try that in the open a couple of times to know exactly how the truck will respond.There's enough power to get the Hybrid (and a 4000-6000 pound trailer) going easily, though it may sound odd at first as the gas engine goes to a certain rpm and stays there while the truck catches up with it.The brakes in a Hybrid will feel touchy at first because they signal regeneration, which adds more retarding without any change in brake pedal pressure.

Driving Yukon models along twisty, two-lane roads on both coasts we found they tracked well through sweeping bends traversed well above the marked 40-mph advisories.Like all large truck-based SUVs, steering is still somewhat slow, but it is precise and offers good feedback and a decent turning circle by truck standards.The handling is also sharper than in the previous generation, due to a stronger and stiffer frame; coil-over-shock independent front suspension; revised, multi-link, live axle rear suspension; and a wider track, by some three inches in front and an inch in the rear.Still, the Yukon is a full-size truck and is prone to body lean in turns and slow reactions in quick changes of direction.

We found the ride to be comfortable and controlled on South Carolina freeways, some of which were glass-smooth while others were buckled from severe winters.With the Denali's available 20-inch wheels, the suspension didn't jolt but you can tell those are heavy truck parts underneath, even on Chicago's notoriously pockmarked streets.The turning circle impressed us.It takes less space to make a U-turn in a Yukon than it does in other SUVs in this class; even some relatively small vehicles such as the Mitsubishi Eclipse need more space to turn around than the Yukon.This is helpful in a world of big SUVs and compact parking spaces.The brake pedal was solid and firm, with a prompt and confident response.

Abundant sound deadening material mutes road noise; you'll hear some from the rear tires only if the stereo is off.That the stereo has to be on for the navigation system to operate is irritating, a strategy shared with expensive Mercedes vehicles.We like that GM vehicles now provide off switches for the daytime running lights and for the inside rearview mirror's auto-dim function.

The 2010 Yukon all-wheel drive models use a single-speed transfer case.If you want a 4WD with low-range gearing, as you might for steep slippery launch ramps or ski resort access, or to tow the Yukon as a “dinghy” behind a motorhome, you have to get an all-wheel drive model with the optional two-speed transfer case.Hybrids have low-range gearing but check with your dealer about towing one as a dinghy.

The available brake controller for trailers with electric brakes (it obviously won't work with surge brakes and may not be compatible with electro-hydraulic disc systems) integrates the brakes on both vehicles for the smoothest, most effective action.

For 2010, Yukon gets more evolutionary updates including E85 compatibility on all 5.3-liter engines, OnStar 8.2 with long-range remote start, active fuel management on the 6.2-liter, a USB port and gearing changes.The GMC Yukon lineup was completely redesigned for 2007.The Hybrid and XFE models were added for 2008, while 2009 brought expanded use of the six-speed automatic transmission, and an integrated trailer brake controller.

Yukon offers power, space, and towing capacity.It can haul large loads of gear, it can survive repeated pounding over rugged terrain, it can pull trailers, all while transporting four in luxurious comfort.

Inside, the Yukon features a simple, elegant dash that hints at aspirations for entry-luxury status.The Yukon has three-row seating standard and can be configured for two to nine occupants.Seating in the first and second rows has plenty of room, but the third row is best left for kids and has to be removed for maximum cargo space.

Engine choices are all V8s.The 320-hp 5.3-liter V8 and Denali’s 403-hp 6.2-liter V8 both have a system that shuts down half the cylinders under light loads to improve fuel economy.For better economy in daily driving look to the Hybrid model which pairs a 6-liter gasoline V8 that switches off completely when not needed, and battery pack with dual electric motors inside the transmission to increase urban fuel economy by 25-30%.

Maximum tow rating ranges from 8100-8600 pounds on standard Yukons to about 6000 on Hybrid models.Most Yukons can carry 1000-1300 pounds of passengers and cargo, which must be subtracted from allowable trailer weight.

Ride and handling characteristics are typical of large SUVs.The Yukon leans in turns and is not agile.The ride quality, on the other hand, is commendable, even with the Denali's available 20-inch polished wheels that add a touch of high fashion trendiness.

All-wheel drive models use Autotrac, a system that can be engaged on dry pavement but does not repeal the laws of physics as some owners believe.Four-wheel drive with low-range gearing handy for rugged terrain, launch ramps, and severe winter weather, is optional.

For those who need a real four-wheel drive with cargo space and towing capacity the Yukon is a competitive choice.Those who don't tow might be better served by a larger crossover like the GMC Acadia, or an all-wheel drive minivan.

In addition to the Tahoe, the Yukon is in the same class as the Ford Expedition, Lincoln Navigator, Nissan Armada, and Toyota Sequoia.Those in need of mileage should put the Hybrid on their shopping list alongside the Lexus RX hybrid, and the diesel versions of the BMW X5, Audi Q7, VW Touareg and Mercedes ML and GL that provide hybrid-like city economy and superior highway economy.

The GMC Yukon SLE 2WD ($38,020) or 4WD ($42,080) comes with a 320-hp 5.3-liter flex-fuel V8 and six-speed automatic transmission.It includes cloth upholstery; dual-zone manual climate control with rear controls; split front bench seat; six-way power driver's seat; 60/40 split-folding second-row bench seat; 50/50 split-fold third row; tilt leather-wrapped steering wheel with radio controls; cruise control; intermittent wipers front/rear; power locks, windows and heated mirrors; remote keyless entry; side assist steps; AM/FM/CD stereo with eight speakers; XM satellite radio; Bluetooth; automatic headlights; theft-deterrent system; roof rails; front recovery hooks; trailer hitch platform with seven-wire harness; one year of OnStar service; and P265/70R17 tires on alloy wheels.The SLE 2 package ($1560) adds three-zone climate control, power front bucket seats with console, and Bose sound system in conjunction with other required options.

Yukon SLT adds leather upholstery; three-zone automatic climate control; Bose six-disc audio system; adjustable pedals; rear park assist; remote start; auto-dimming inside mirror; and universal garage door opener.SLT2 adds more adjustable heated front seats, driver memory system, heated second row seats with power seat release, power-operated liftgate and outside heated power-adjustable, power-folding mirrors.

Yukon Denali 2WD ($53,000) and 4WD ($55,995) upgrade to a 403-hp 6.2-liter engine, 12-way power front seats; heated front and second-row seats; driver memory system; power tilt, heated, wood-and-leather steering wheel; Autoride suspension; power liftgate; power-folding reverse-tilt mirrors; auto-dimming inside and driver's side mirrors; chrome trim and unique grilles; Bose Centerpoint audio system; rain-sensing front wipers; and 20-inch polished aluminum wheels with 275/55 tires.Available only on Denali is a side blind zone alert system ($500).

Yukon Hybrid 2WD ($51,185) and 4WD ($53,995) are well-equipped, slotting between SLT2 and Denali for features and amenities.However, the Hybrid does come standard with a 6-liter V8 gas engine and electric drive system contained within the transmission that rate 332 hp and 367 lb-ft of torque, navigation system with rearview camera, locking rear differential, and P265/65R18 low-rolling resistance tires on alloy wheels.It does not have roof rails, fog lamps, tow hooks, or a separately-opening glass on the liftgate.Hybrid mechanicals are warranted for 8 years or 100,000 miles.

Yukon Denali Hybrid 2WD ($58,500) and 4WD ($61,345) feature Denali trim with the hybrid powertrain.Options are limited to a spare tire/wheel ($995), moonroof ($995), rear entertainment ($1295) and blind zone alert ($500).

Options include 20-inch wheels ($1795); three-zone climate control ($195); and audio and entertainment system upgrades.More choices include a moonroof ($995); retractable side steps ($1095); trailer brake controller ($200); rear DVD entertainment ($1295); Z71 Off-Road package ($1830); second-row bucket seats ($490 plus $425 for power release) and engine block heater ($75).Yukons that come with second-row buckets may often be ordered with a 60/40 second-row bench at no charge, and larger wheels can often be downsized to standard 17-inch at no cost for rough roads, tire chain clearance, and so on.

Safety features that come standard on all models include dual-stage front airbags; three-row, head-protecting curtain side airbags with rollover sensors; four-wheel antilock brakes; StabiliTrak stability control system with rollover mitigation; LATCH child safety seat anchors; and a tire pressure monitor.Optional are rearview cameras, rear park assist, and Denali’s side blind zone alert.

The one-piece front end presents a friendly, welcoming face but without forfeiting the Yukon's presence.Large headlight housings are vertically oriented rather than the Tahoe's horizontal layout.The trademark grille with ruby-red logo and lower air intake ensure plenty of engine cooling.

Door handles bridging deep recesses make for easy gripping in all seasons.Squared-off wheelwells carry forward a Yukon signature styling cue.They suggest trimming up with the available 20-inch wheels and tires, though that's not our choice from a driving and towing perspective.

At the rear, a broad, mostly flat, almost vertical tailgate resides between tall, narrow taillights.The independently hinged rear window is a nice touch, permitting easy loading of grocery bags and such.

The Yukon Hybrid has several styling cues that distinguish it from the other models.To counter added weight (the Hybrid is roughly 250 pounds heavier than standard) and drag, the front end features an aluminum hood and bumper beam, and a more prominent air dam you might scrape on steep driveways, never mind off-road travel.The upper grille is expanded while the lower is smaller and openings that would house fog lights and tow hooks are blocked off.Along the sides, the running boards are reshaped for improved aerodynamics and the wheel flares are slightly reshaped.At the back, the rear pillars, spoiler and center high-mounted stoplight have a unique shape, the tailgate is made of aluminum and has fixed glass, and LED taillights replace the standard bulbs.The wheels are more aero efficient and the tires have lower rolling resistance.The spare tire and jack have been replaced by a tire inflation kit; a spare is optional.The result is a slightly better coefficient of drag to help improve fuel economy, if only by small amounts.

We think the Yukon dashboard is a friendlier, slicker and more integrated assemblage of gauges, display screens, touch pads and control panels than those in either a Land Rover or the Mercedes-Benz GL- and ML-Class.The GMC's gauge cluster is very informative, reporting via secondary analog gauges powertrain data others leave to warning lights or bury in scrollable information displays.

Leather surfaces feel expensive, if not luxurious.The fit between panels and coverings is impressive, with tight tolerances.Less impressive is the finish of some of the hard plastic surfaces, which look better than they feel; lighter-color interiors convey the lux look much better than the dark colors.The headliner is a woven fabric that looks and feels like mouse fur.

The Hybrid model has a unique gauge cluster with a special tachometer and an economy gauge.The economy gauge can be used for more efficient driving (as can be the mpg data on most models' info display in the tachometer).Note that economy is best with the gauge pointed in the left-to-straight-up range that translates on other gauges to cold engine, low oil pressure, and low fuel level.The tachometer has an Auto Stop reading to indicate when the gasoline engine is shut off.No Yukon tachometer has redline because the scale ends at the engine's maximum speed.

The Hybrid comes standard with a navigation system and a 6.5-inch screen that shows a graphic representation of the hybrid system's power flow.This screen shows if the power is coming from the electric motors, the gasoline engine, or both, plus when regenerative braking is charging the batteries.The system also shows if the vehicle is in two- or four-wheel-drive mode.It's fun for passengers to monitor these readouts; they help you learn about how the hybrid system works and show when it is being used for the best fuel economy, but care must be taken by the driver to not be distracted by them.

The design of the Yukon's dash gives the driver an expansive view out the windshield, adding to the feeling of being above it all.Visibility is good all around, though the imposing right side C-pillar (the post between the rear side door and the rear quarter panel) does nothing to reduce the large side mirrors' blind spot.Along the same lines, the third-row seat blocks the lower third of the rear window; folding the third row down eliminates this.

The front seats are refreshingly comfortable and easy to adjust; most models have electric seat cushion adjustment but manual recline adjustment.They offer good thigh support, which is sometimes lacking in GM vehicles.Adjustable pedals on some models take the place of a telescoping steering column, and the tilt wheel is angled slightly away from the centerline of the car.

The available second-row captain's chairs offer good thigh support as well.We're disappointed with the folding armrests, however; they have one setting, which won't fit every occupant.Some way to adjust the angle of these armrests would be welcome.The Hybrid model has thinner front seats that reduce weight and open up more than an inch in second-row knee room.We found them to be just as comfortable as the standard seats.

Room for people is respectable and competitive with other full-size SUVs.In front room measurements, the GMC Yukon equals of betters the Ford Expedition, Nissan Armada, and Toyota Sequoia but all have plenty of space.Trying them on will show which ergonomic setup and volume suits you best.

In the second row, the Yukon trails the Expedition and Armada in headroom and legroom and betters them in hiproom, but by less than an inch in all regards; it also slightly trails the Sequoia in second-row headroom, but has slightly more hiproom and considerably more legroom.In other words, all large SUVs have a lot of second-row space and the Yukon is no exception.As for second-row access, the Yukon suffers from small-feet syndrome, where the clearance between the base of the second row seat and the doorframe is so cramped, it's impossible to step in or out without turning your foot sideways.

Since the third-row seats sit on the cargo floor third-row legroom is limited in the Yukon, with little space for adult feet and knees up at chest level.The Expedition, Sequoia, and Armada offer considerably more legroom for third-row passengers; the Expedition has more than a foot more third-row legroom and is very close in all other respects.On the upside, it's surprisingly easy to climb in and out of the Yukon's rearmost seat, the walk-through opening notably larger than entering the second row.The second-row seat folds up out of the way with the release of a lever on the outboard pivot, or optionally, at the press of a button with the optional power-fold feature.Unfolding the seat is done manually, however.Make sure it's securely latched.

Cargo space behind the third row is limited, with just 17 cubic feet, less than any of the three competitors.With the second- and third-row seats out of the way, the Yukon offers comparable cargo space for the class, squeaking by the Expedition, exceeding the Armada's space by more than 10 cubic feet, but losing to the Sequoia by almost 12 cubic feet.Of course, the extended wheelbase Yukon XL (and Expedition XL/Navigator L) make up for any of the space deficiencies versus the Armada and Sequoia.

One area where the Yukon really falls down is the ease with which cargo room can be optimized.Both the Sequoia and Expedition offer a power-folding third row that folds flat into the floor.For optimum cargo room in the Yukon, the third-row seats must be removed, and they are heavy, bulky and you need someplace to store them.

Cubby storage includes a compact glove box, fixed map pockets with molded-in bottle holders on the front doors, and pouches on the backs of the front seatbacks.A large bin with removable double cup holder is provided between the front seats.In the Yukon Denali, this feature is separated into a storage bin and twin cup holders, both with hinged covers and surrounded in wood trim.Ordering the front bench seat for three-across seating eliminates the center console, of course.

NewCarTestDrive.com correspondent G.R.Whale contributed to this report from Los Angeles, with Tom Lankard in Georgia, and Kirk Bell in Chicago.