WICKENBURG, Ariz. -- Cutting a straight swatch across pancake flats in the Sonoran Desert west of Wickenburg, Ariz., the slab on U.S 89 becomes our track to sample the massive firepower and over-the-top luxuries built into the redesigned 2015 GMC Yukon XL sport utility vehicle dressed in deluxe Denali trim.
The XL edition -- as in "Extra Large" -- happens to be one of the largest SUVs on the market, save for GM sister ships like Chevrolet Suburban and Cadillac Escalade ESV.
And Denali -- a name drawn from native Alaska Athabascan people to describe "the High One" of Mt. McKinley, tallest peak on the North America continent -- represents the pinnacle trim for Yukon XL in a leather-lined issue charged with class-capping horsepower.
It's a grand wagon of super-size scale and measures even larger than a full-size Yukon.
Overall length of the XL edition exceeds a full-size Yukon by 20.4 inches, and there's about 14 inches of extra space applied lengthwise at the rear of the cavernous cabin which contributes more legroom for riders on third-row seats and almost three times the cargo space (at 39.3 cubic feet) behind the third seats.
Yukon XL Denali of 2015 vintage is an all-new fourth generation rendition. It has the same 121-inch wheelbase length as 2014 models but the overall length and width expand slightly to bring additional wiggle room to the vast passenger compartment.
Its tip-to-tail remake is based on a new platform from General Motors. The architecture starts with boxed frame rails stretching the length of the vehicle for a rock-solid and rigid foundation using high-strength steel and hydroforming to provide greater strength and rigidity with less weight. A revamped cab structure integrates high-strength steel in A and B pillars as well as roof rails and rocker panels, while ultra-high-strength steel segments show up in rocker panels to add protection for offset collisions.
You can't miss the square-jaw prow sporting a massive chrome-accented grille and flanking lamp clusters housing GMC's signature C-shaped LED light tubes and HID headlamps.
Check beneath Yukon XL Denali's square-cornered hood to uncover a new EcoTec3 aluminum-block V8 engine which displaces 6.2 liters and applies GM's Active Fuel Management (AFM) technology which cuts by half the number of cylinders engaged in the combustion process when boosted power is not needed to conserve fuel.
The big-beef plant produces 420 hp at 5600 rpm and huge torque of 460 lb-ft at 4100 rpm with all of that muscle translated through GM's electronically controlled Hydra-Matic 6L80 6-speed automatic transmission.
Trailering capacity climbs to 8100 pounds.
GMC configures the 2015 Yukon XL Denali with rear-wheel 2-wheel-drive or 4-wheel-drive traction. The new 4WD mechanism brings set-it-and-forget-it automatic activation all-wheel-drive.
All Denali editions carry GM's Magnetic Ride Control (MRC) variable suspension device which controls wheel and body motion magnetically to effect continuously variable shock damping.
A rack and pinion steering system gets electric power assistance, which contributes to powertrain fuel efficiency.
Brakes include a disc at every wheel -- ventilated front and rear -- with Duralife brake rotors and linkage to a 4-wheel anti-lock brake system with electronic traction and skid controls with added trailer-sway control.
Yukon XL Denali's redesigned passenger compartment is quieter, more comfortable and better-connected than previous editions, providing three rows of seats to accommodate as many as eight riders.
There's a pair of buckets on the front row, a second tier with two fold-down captain's chairs plus a third bench with 50/50-split that for the first time also folds flat via push-button power-folding feature.
New technology perks range from multiple USB ports and power outlets (including a 110-volt 3-prong outlet) to OnStar connectivity with 4G LTE and WiFi hotspot, a keyless entry device with push-button starter, and an 8-inch color touch screen radio with MyLink connectivity.
We estimate MSRPs hit $65,380 (2WD) and $68,380 (4WD).