2012 GMC Sierra Hybrid Review

GMC Sierra 1500 Hybrid is the only hybrid in the full-size pickup segment, delivering an estimated 23 mpg on the highway and 20 mpg in the city (2WD and 4WD models). Compared with non-hybrid models, that's 33 percent greater city fuel economy and a 23.5-percent improvement in overall fuel economy.

2012 GMC Sierra Hybrid photo -

Sierra Hybrid achieves its efficiency without compromising the capability customers expect in a full-size truck – including up to a 6,100-pound (2,767 kg) trailering capacity.

2012 GMC Sierra Hybrid photo

Power for the Sierra Hybrid comes from General Motors’ patented two-mode hybrid system and a powerful 6.0L gas V-8, which combine to deliver all-electric driving up to 30 mph (48 km/h). The system saves fuel using electric propulsion, even when towing a trailer.

2012 GMC Sierra Hybrid photo

The Sierra Hybrid is offered in the crew cab body style on both 2WD and 4WD models, with 3HA and 3HB trim levels. All models are equipped with StabiliTrak electronic stability control system, a locking rear axle and a trailering package. It also includes standard dual-stage frontal air bags, head curtain side air bags and seat-mounted side impact air bags.

2012 GMC Sierra Hybrid photo

Changes for 2012 include a chrome, three-bar grille, a new hard-drive navigation radio and a new exterior color. Quicksilver Metallic.

Hybrid system details

GM’s advanced Electrically Variable Transmission (EVT) and 300-volt nickel-metal hydride Energy Storage System (ESS) work in concert with the standard 6.0L V-8 gasoline engine with Active Fuel Management (AFM) and late intake valve closing (LIVC) technology to enable the Sierra Hybrid’s efficient performance. This hybrid system not only enables the Sierra to launch and drive up to 30 mph on electricity alone, it also allows the 6.0L V-8 engine to operate in its more economical V-4 mode for longer periods.

GM designed the EVT to provide the best combination of city and highway fuel economy. Used with the Vortec 6.0L V-8 engine with Active Fuel Management, it is an all-purpose system well-suited to provide excellent economy and full-size pickup passenger-carrying, cargo-hauling and trailer-towing capabilities.

2012 GMC Sierra Hybrid photo

The EVT is designed to bolt directly to the standard four-wheel-drive transfer case found on the gasoline-only models for true four-wheel-drive capability. The following major components comprise the Sierra Hybrid’s unique powertrain system:

Electrically Variable Transmission (EVT)
Energy Storage System (ESS)
Vortec 6.0L V-8 with Active Fuel Management (AFM) and late intake valve closing (LIVC).
Electronically variable transmission (EVT): The key to GM’s EVT is its unique assemblage of two 60 kW electric motors, three planetary gearsets and four traditional hydraulic wet clutches. This arrangement allows continuously variable operation, and provides four fixed gear ratios (with operation comparable to that of a standard electronically controlled automatic transmission).

A sophisticated Hybrid Optimizing System constantly receives torque-based data from the powertrain and other vehicle systems, and determines the most efficient means of propelling the vehicle — either via electric power, gasoline engine power or a combination of the two. The EVT is like having two transmissions in one — continuously variable drive for light-load conditions and fixed-ratio drive for high-load situations.

Energy storage system (ESS): A 300-volt nickel-metal hydride Energy Storage System (ESS) provides power to the EVT’s two electric motors. This battery pack is located under the second-row seat.

In addition to supplying power to the EVT, the ESS also provides power to the air conditioning compressor and the Accessory Power Module (APM), which converts the high-voltage supply to 42 volts for the electric power steering system, and 12 volts for the vehicle battery and other 12-volt electrical accessories.

2012 GMC Sierra Hybrid photo

Battery pack durability and reliability are maintained via optimized charge and discharge cycles, as well as a dedicated cooling system that draws air from the passenger compartment. As part of the vehicle’s emission control system, the ESS is warranted for eight years/100,000 miles.

Vortec 6.0L V-8 engine: Engineers chose the Vortec 6.0L V-8 gasoline engine for the Sierra Hybrid because of its favorable torque characteristics. This is especially important because GM engineers adapted the 6.0L V-8 to operate with late intake valve closing (Atkinson-cycle combustion process) for reduced pumping losses and better overall fuel economy.

Using flat-top pistons, cylinder heads borrowed from GM’s 5.3L high-output V-8 and a 10.78:1 compression ratio, the Vortec 6.0L V-8 produces 332 horsepower (248 kW) at 5100 rpm and 367 lb.-ft. of torque (495 Nm) at 4100 rpm, yet requires only regular unleaded fuel.

The Vortec 6.0L also features variable valve timing to control late intake closing, as well as Active Fuel Management, which allows four of the eight cylinders to be shut off during periods of light load. With the benefit of electric boost, the engine is able to stay in V-4 mode for longer periods in the Sierra Hybrid.

Auto Stop mode and regenerative braking

A key contributor to fuel economy is the gasoline engine’s Auto Stop mode. At vehicle speeds between 0 and 30 mph, the gasoline engine may be automatically shut down. By leaving the engine off and allowing the vehicle to move only under electric power up to 30 mph, such as during heavy stop-and-go traffic, fuel consumption is greatly reduced.

The regenerative braking system works in concert with the hydraulic braking system. The system uses a brake pedal emulator, which provides progressive resistance as the pedal is depressed. This consistent pedal feel is very much like that of a standard hydraulic braking system in operation.

Quiet performance

Sierra Hybrid matches its gasoline-only siblings in comfort and convenience, with special attention paid to acoustic details that makes for a very quiet driving experience. Examples include:

Exhaust system and resonator specially tuned for the 6.0L LIVC engine’s Active Fuel Management operation. It ensures comfortable interior acoustics and a pleasant exhaust note during both V-4 and V-8 operation
Additional engine intake induction tuning for reduced interior noise and pleasing sound quality
Low-rolling resistance, “quiet-tuned” P265/65R18 tires for reduced road noise
Electrically driven, 300-volt air conditioning compressor reduces vibration and allows the HVAC system to cool the passenger compartment even when the gasoline engine is shut off
Electrically driven, 42-volt variable-assist power steering reduces vibration and provides up to a 0.5-mpg fuel economy improvement by reducing parasitic losses common in belt-driven hydraulic systems
Energy Storage System (ESS) cooling system internal fan is tuned to be quiet at low vehicle speeds when the fan could more easily be heard by the occupants.
Sierra Hybrid interior features

A unique hybrid gauge cluster includes a special tachometer incorporating an Auto Stop position just above the 0 rpm mark that indicates when the gasoline engine is in shut-down mode. An analog economy gauge, to the left of the tachometer, helps the driver maintain the most efficient driving style.

Located midway down the center stack, the available navigation system’s 7-inch full-color VGA display (3HB models) doubles as a monitor that shows a graphic representation of the hybrid drivetrain’s power flow. This display continuously informs the occupants how the system is sending power to the wheels from the ESS/electric motors, the gasoline engine or both. The screen also displays reverse electrical flow during regenerative braking and whether the vehicle is in two- or four-wheel-drive mode.

Sierra Hybrid exterior features

Grille with chrome surround is standard on all models.
Chrome front and rear bumpers are standard are all models.
Heated, power-operated outside mirrors including auto-dimming, integrated signal indicators, ground lights and curb-tilt feature are standard on 3HB. Heated and power-adjustable mirrors are standard on 3HA.
Spring-loaded “EZ-Lift” locking tailgate is standard on all models.
Body-color side moldings are standard on all models.
Eighteen-inch aluminum wheels and P265/65R18 all-season tires.
Exterior color choices include: Onyx Black, Midnight Blue Metallic (late availability), Mocha Steel Metallic (late availability), Stealth Grey Metallic, Steel Grey Metallic (late availability), Summit White, Fire Red, Quicksilver Metallic and Carbon Black Metallic (late availability).
Sierra Hybrid interior standard and available features

Dual-zone automatic climate control is standard on all models.
SiriusXM Satellite Radio standard on all models.
AM/FM stereo with MP3-compatible CD player is standard on 3HA.
Navigation radio with MP3-compatible CD player and USB port is standard on 3HB and includes SiriusXM NavTraffic compatibility.
Bluetooth phone connectivity is standard.
Power-adjustable pedals are standard on 3HB.
Two auxiliary 12-volt power outlets are standard on all models.
Leather-appointed front seating is standard on 3HB.
Front 40/20/40-split bench seat is standard on 3HA.
Front bucket seats are standard on 3HB and include six-way power driver and passenger seat adjusters and floor console.
Three-passenger, full-width folding bench seat is standard on all models (includes child seat top tether anchor).
Leather-wrapped steering wheel with audio controls is standard on all models.
Power-operated sunroof is available on 3HB.
Sierra Hybrid chassis and suspension

The Sierra Hybrid is built on GM’s full-size truck platform, incorporating a fully boxed frame, coil-over-shock front suspension, leaf-spring rear suspension and rack-and-pinion steering.

Wide front and rear tracks – 68.1 inches (1,732 mm) front/67 inches (1,702 mm) rear – enhance handling and vehicle stability for a more confident road feel.
A stiff frame reduces vibrations transmitted to the passenger cabin, while the strength and accuracy of the fully boxed frame also enable precise mounting and tuning of chassis and suspension components.
Autotrac electronic transfer case with rotary controls is standard on 4WD models.
The standard axle ratio is 3.08.
A locking rear differential is standard.
7,100 GVWR on 2WD models.
7,300 GVWR on 4WD models.
A trailering package is standard on all models.

2012 GMC Sierra Hybrid photo

Sierra Hybrid safety and crash-avoidance features

Standard head curtain side air bags with rollover protection for both seating rows. The roof-mounted head curtain air bags include design features that provide increased rollover protection and occupant containment.
Standard seat-mounted side-impact air bags for driver and right-front passenger provide thorax and pelvic protection.
StabiliTrak electronic stability control system helps reduce the risk of rollover crashes by keeping the vehicle in the driver’s intended path by applying throttle, braking or a combination of both.
Rear vision camera system is designed to provide the driver with
a view of people or objects in the rearward path of the vehicle. It is standard on 3HB models.
Standard four-wheel-disc brake system with ABS featuring smooth, quiet operation, longer pad life and more resistance to brake pulsation.
Pretensioners minimize forward movement during a collision, and are standard on the front safety belts. Load-limiting retractors cinch the belt more tightly.
Tire pressure monitoring system, standard on all models.
Standard remote keyless entry (RKE) system provides a second function for the red panic button. Drivers can use it to locate their cars without sounding the panic alarm.
Strong body structure to absorb crash energy and provide a protective “safety cage” around occupants.