General Motors Focuses on Fuel Savings for Chevy and GMC Trucks

Both the Chevy Silverado and GMC Sierra powertrains deliver enhanced fuel economy. "We have improved our fuel efficiency for 2010 pretty much across the board," states Tony Truelove, marketing manager for the Chevrolet Silverado.

One contributor is the development of a fuel saver mode, which allows the trucks to make better use of GM's Active Fuel Management system. "The fuel saver mode is built into the calibration of all of our 5.3-liter engines," says Truelove. It enables more aggressive active fuel management by running the engine on four cylinders in light throttle conditions vs. eight.

"The fuel saver mode is a calibration that keeps the engine in four-cylinder operation longer to improve fuel economy," adds Carl Hillenbrand, Silverado product manager. "From a hardware perspective for 2010, there is not anything significantly changed [with the engines]."

A prime enabler of this technology has been the switch to six-speed transmissions across the product line. This allowed a more aggressive calibration for the active fuel management than was possible with the previous four-speed transmission.

"We are trying to make it seamless to the customer, so that he can't feel it switching back and forth between cylinders, while giving the best fuel efficiency," states Truelove.

Gearing options help to save fuel, as well. "We introduced a 3.08 axle ratio," says Truelove. "The 3.42 is our big axle and the 3.08 is for customers who want to get even more fuel efficient. It still offers a respectable towing rating and you are getting real-world fuel economy."

The 2010 Silverado 1500's range of 4.8L, 5.3L and 6.2L V8 engines also offers E85 capability, while the 4.8L and 5.3L now feature variable valve timing.

The Chevrolet Silverado Hybrid, introduced earlier this year, is a full-size pickup offered in a crew cab body style on both 2WD and 4WD models. It achieves 40% greater city fuel economy and a 25% improvement in overall fuel economy, while delivering the capability expected of a full-size truck, including a 6,100-lb. towing capacity.

The Silverado Hybrid pairs up General Motors' patented two-mode hybrid system and a powerful 6.0L gas V8 to deliver efficient performance. All-electric driving up to 30 mph saves fuel even when the truck is fully loaded or towing a trailer. EPA-estimated fuel economy for both 2WD and 4WD models is 21 mpg city and 22 mpg highway.

"To get well over 300 hp and 22 mpg - certainly, if you made that claim a couple of years ago, people would have laughed at you," says Brian Goebel, Chevrolet communications. "From a competitive advantage standpoint, we think that is pretty significant."

The Electrically Variable Transmission (EVT) incorporates grade braking and tap up/tap down shift control. It proves beneficial when towing on curves or lower-speed back roads, since smooth gear transitions eliminate the "shift shock" torque disruption that can occur during abrupt shifts, such as when slowing or braking.

GMC Sierra and Chevrolet Silverado 2500 and 3500 models are available with a Hydra-Matic 6L90 six-speed automatic transmission matched with the 6.0L engine, giving the powertrain a maximum gross combined weight rating (GCWR) of 18,500 lbs. The 6L90's wide, 6.04:1 overall ratio - including two overdrive gears - helps deliver a balance of performance and fuel economy. It also offers manual range selection and tap up/tap down control.

The DuraMax 6.6L turbo-diesel engine continues in the lineup, as well. It offers power ratings of 365 hp and 660 lbs.-ft. of torque and is mated to the Allison six-speed transmission, giving the diesel truck a maximum gross combined weight rating of 23,500 lbs.

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