General Motors Corp. will announce on May 21 that it will add more fuel-efficient V8 engines in its light trucks starting in 2004, increasing mileage by as much as 25 percent, according to a May 20 Reuters story by Michael Ellis. The new engines, part of GM's efforts to maintain its advantage in truck fuel-efficiency over rival Ford Motor Co., resurrect "displacement-on-demand" technology, which automatically shuts off half of the V8's cylinders, temporarily turning it into a more efficient four-cylinder, when the trucks are cruising at a constant speed or carrying a light load. During acceleration or when pulling a heavy load, all eight cylinders do the work. GM plans to manufacture more than 150,000 of the V8 engines in 2004, and increase production to nearly 1.5 million units annually by 2007, according to Reuters. Increases would range from 1 to 4 miles per gallon on GM truck V8s, and a 2-mpg increase should be common, GM estimates. GM sells at least 1 million V8 trucks a year. If they average 10,000 miles a year, a 2-mpg increase would save 89 million gallons of gas a year, worth $152 million at today's prices. DOD technology will be standard, not optional, beginning with the introduction of redesigned full-size pickups and SUVs in 2003, and it coincides with reworked truck V8s to be launched the same time. GM's light truck fleet, weighted by sales, averaged about 21 miles per gallon last year. The new engines would be put in its larger vehicles, which are less fuel efficient, such as the Chevrolet Suburban full-size SUV, which presently gets between 14 and 18 miles per gallon. Reuters quoted Sam Winegarden, GM's chief engineer of Vortec V8 engines, as saying the split-second transition from V8 to a four-cylinder is unnoticeable and vastly superior to when GM's Cadillac division briefly tried a displacement-on-demand engine in 1981. That engine, which shifted between a V8, a six-cylinder and a four-cylinder, depending on the driving conditions, lasted only about one model year because it shook uncontrollably and the technology was much more costly. GM officials have been annoyed by Ford's efforts to cast itself as an environmental leader, and have taken more steps to point out their own contributions to raising fuel efficiency and cutting vehicle emissions and pollution. Meanwhile, pressure is mounting on the U.S. government from environmental groups to raise the required fuel efficiency to the same level as cars. President Bush's energy plan, announced last week, said the government will reexamine federal fuel economy standards, with an eye toward raising them "without negatively impacting the U.S. automotive industry." The new V8 engines will boost fuel economy by up to 25 percent in certain driving conditions. However, the listed fuel economy will rise by about 8 percent, based on the testing procedures required by the U.S. Environmental Protection Agency, which simulates rush hour traffic. GM officials said the company is also considering applying displacement-on-demand technology on some of its six-and four-cylinder engines. Currently, DaimlerChrysler AG's Mercedes is the only major automaker to offer displacement-on-demand engines, making it available on V12 engines for its high-end S600 and CL600 sedan and coupe, which each cost more than $110,000. The engines automatically deactivate half the cylinders, effectively making it into a six-cylinder, when full power is not required. Mercedes also sells a luxury sedan in Germany that has the technology on a V8. Ford, which said last July that it is aiming to boost the fuel efficiency of its SUVs by 25 percent by 2005, is also considering similar technology for its V8 and/or V10 truck engines, according to company officials.