Not Firing on all Cylinders - GM Displacement on Demand

That phrase usually implies a bad thing, but not in this case. The 2005 GMC Envoy XL, Envoy XUV, and Chevrolet TrailBlazer EXT will be the first vehicles to showcase GM’s Displacement on Demand fuel-saving technology later this year. Displacement on Demand, which saves fuel by using only half an engine's cylinders during most normal driving conditions, will be a standard feature in the vehicles' optional Vortec 5300 V-8 engines, expanding to V-6 engines later. The system makes full power available automatically whenever needed so performance and cargo carrying ability aren’t compromised.

We had the opportunity to drive a Displacement on Demand equipped SUV and found the system to work seamlessly as it switched back and forth from eight cylinders to four. According to EPA, this technological twist will help boost the fuel efficiency of these larger vehicles by about 8 percent, but could result in as much as a 25% bump upward under real-world driving conditions, says GM. More than 150,000 of these more fuel-efficient engines are expected to be produced in the first year with up to two million by 2008.