Evolution brings more fuel-efficient vehicles, including crossovers and GMC’s highest-volume vehicles, the Sierra pickups

GMC has been manufacturing trucks in the U.S. since 1902, and lately has added models and improved on content and technology, resulting in the impressive lineup available today.

That evolution brings more fuel-efficient vehicles, including crossovers and GMC’s highest-volume vehicles, the Sierra pickups.

Sierra is the most powerful light-duty pickup available, and also the first full-size pickup to be given a five-star safety score from the National Highway Traffic Safety Administration since the new-vehicle assessment program was changed in 2010.

There also are four heavy-duty (HD) Sierra models, featuring two Denali trims, priced from $32,420 for the 2500HD to $51,925 for the high-end 3500HD Denali.

A Duramax 6.6-liter turbo-diesel engine is available for all HD models, and is paired with an Allison 1000 six-speed automatic transmission. GMC has sold more than 1.5 million of the Duramax/Allison combo since it was introduced in 2000.

The light-duty, or 1500 series, Sierra was completely redesigned for 2014, and now the heavy duty Sierra gets its own makeover for model year 2015. The Sierra HD’s interior is all-new and better connected, moving up from the 2014 Sierra 1500.

Outside, there is bold new styling, and the lineup includes a new double cab and revised crew cab.

My tester, the Sierra HD Denali, comes only as a crew cab with all the top-notch interior amenities and all-out heavy-duty abilities.

All cabs have larger rear doors and new seat designs for easier entry and exit. Assist handles on the pillars help shorter people to climb in. The crew cab also has two more inches of legroom in the rear. Sierra now has more storage compartments, more plug-ins for portable devices and next-generation GMC Intellilink with eight-inch color touch screen.

Available is a built in hot spot, which, along with standard OnStar (with 4G LTE), provides more connectivity than ever. With available 6-foot-6 or 8-foot cargo boxes, (depending on model), integrated heavy-duty trailering equipment (capable of pulling up to 19,000 pounds; 23,200 with a fifth-wheel or gooseneck), and powerful gas or Duramax diesel powertrains, the Sierra HD can work hard.

The Duramax is able to go for at least 200,000 miles in rough-duty mode without a major overhaul. An expanded bi-fuel option now allows the gas engine to use compressed natural gas.

Although no EPA estimates were available (not required for big pickups), my Sierra HD Denali averaged 17.5mpg during my test.

Also new is the Sierra HD’s corner step rear bumper (taken from the 2014 Sierra 1500), an easy lift-and-lower tailgate with lock, movable upper tie-downs, trailer sway control, cruise control, auto grade braking and diesel exhaust braking (reduces brake wear on grades), and advanced engine cooling airflow (to better maintain full power under heavy loads and high outside temperatures).

A diesel exhaust brake restricts the exhaust flow from the engine, creating back pressure which slows engine speed to offer supplemental engine braking, often without ever applying the manual brake – even in a heavily-loaded vehicle on a steep downgrade.

My attention-grabbing four-wheel-drive Sierra 2500HD Denali in Summit White ($53,740), came with a Duramax Plus Package for $8,845, which included the turbo diesel engine and Allison transmission; lane-departure warning; forward collision alert; and safety-alert driver’s seat. The Duramax package also added an engine-block heater and upped the gross vehicle weight limit to 10,000 pounds.

This truck is easy to see ( very big) and recognize, with a large rectangular signature chrome grille and a power-dome hood featuring Duramax/Allison chrome badging. My Denali also had unique interior trim with a soft-touch instrument panel and "Denali" script on the bright door sills and embossed onto the front seatbacks.

Besides the grille, the Denali had chrome across the lower middle of the front bumper, around the fog-light and headlight housings; chrome hub cover, body-side molding and six-inch tubular chrome assist steps with textured rubber pads for sure footing; lower side-window trim and door handles; and Sierra badging on the tailgate.

The exterior also had black fog-light housings, front air intake and ground effects; wheel-arch molding with molded splash guards; front and rear bumper steps; side mirror housing and arms; satellite antenna; taillight surround; and tailgate handle.

On my Denali, standard 18-inch polished aluminum wheels were replaced by 20-inch forged polished aluminum wheels for $850, and all-terrain blackwall tires took the place of standard all-season tires for $200 more.

My tester had body-color bumpers with integrated recovery hooks in the front, LED cargo lighting, a sprayed on bedliner, bed-rail protectors, and projector headlights with signature LED daytime running lights within the headlight housing.

The interior was Cocoa and Dune with leather heated (seat and back) and cooled (seat only) front bucket seats with 10-way power adjustment including lumbar; two-position driver’s seat memory; adjustable headrests; and a 60/40 folding rear bench seat (folds up rather than down, to open up the rear for large items).

An under-seat storage package for $230 can be used to corral small items. The leather-wrapped steering wheel with multiple controls was heated, and the power sliding rear window had a defroster.

Inside, small touches of chrome trimmed the dials, speakers, and vents, door handles and cupholders, the armrest handle and the rim of the recessed cubby in the center console. Light bronze-color metallic trim surrounded the vents, the control panel and the cupholders, and finished the steering-wheel spokes. Wood trimmed the sides of the center console and the middle of the door panels.

Denali’s interior is not only attractive, it is high-tech with an exclusive eight-inch driver-information display to show vehicle settings, audio, and navigation information on a screen in the center of the instrument panel – reconfigurable to suit the driver.

GMC’s IntelliLink connectivity controls audio features, navigation, Bluetooth phone features, a Pandora app using the eight-inch color touch screen on the center stack or Natural Language Voice Recognition. The navigation system has all-new map displays. Satellite radio is also included, with a three-month trial subscription.

Sierra comes with six months of OnStar Directions and Connections with automatic crash response, roadside assistance, emergency services, remote door unlock, and turn-by-turn navigation, plus a five-year basic plan.

My tester had five USB ports, three 12-volt outlets (one on the back of the center console), and one AC outlet to accommodate almost anything electronic the driver/passengers need or want.

With the deep cubby under the front armrest, which has file hangers built into the sides; the two-layer cubby at the front of the armrest, with slots to hold small supplies or portable devices; a shallow rubber tray on the center armrest; and the dual glovebox, with a shallow tray in the upper level, the cockpit becomes an office on wheels.

On an extended drive, we found the Sierra comfortable and roomy with 45.3 inches of legroom in the front and 40.9 inches in the rear. Headroom was impressive with 42.8 inches in the front and 40.5 in the rear. The dual-density foam seats are designed for comfort over long drives and to stay great looking after years of use.

Rear passengers had a fold-down center armrest with two cupholders, two map/bottle pockets and a third cubby on each door, two cubbies on the back of the front console, and pockets on the back of the front seats. All three positions had lower anchors and upper tethers for child safety seats. Even the middle seat was adequate for a small adult.

Part of our weekend drive involved one-lane, two-way roads on the side of mountains with some steep grades. Sierra’s multi-level four-wheel drive is controlled by a simple knob to the left of the steering wheel and came in handy more than once, as did the hill-start assist and hill-descent control.

My Sierra came with GMC’s exclusive Duralife brake rotors – hardened using a patented process for extra strength and protection from corrosion, to nearly double the life of the rotors.

The standard rearview camera also helped us out of a tight spot a couple of times and can also be used when backing up to a trailer. Front and rear park assist helped avoid objects when turning tight corners (the road had lots of hairpin turns) and performing multi-point turn-arounds.

We didn’t use the standard integrated tow package, capable of pulling 13,000 pounds, but the optional power camper mirrors (with separate wide-angle section, daytime running lamps and reversing lights, heat and turn signal, $55) helped avoid the edge of the narrow road several times.

Sierra comes with underbody shields, a trailer brake controller, and auto-locking rear differential.

My Sierra had power-adjustable pedals – perfect for a small person driving a large truck. An optional power sunroof added $995, and a dual alternator (300 amps total) added $295, bringing the total of options to $11,240.

The sticker of my tester included a $1,500 Duramax package discount and $1,095 destination charges, for a total delivered price of $64,575.

Contact freelance automotive columnist Emma Jayne Williams at emmajayne1948@gmail.com .