cylinder deactivation 
Most six- and eight-cylinder engines need only the power of a couple of cylinders to keep the average vehicle cruising at normal highway speeds. With that in mind, Cadillac attempted a cylinder deactivation scheme in the 1980s that chose either four, six, or eight cylinders to move the car, depending on engine load. Unfortunately, the processor doing the choosing wasn't that reliable, and the cylinder changeover was somewhat abrupt.

New electronics and engine management controls allow a reliable, seamless deactivation, with an improvement in fuel economy. GM has launched its newer technology on light trucks, and other manufacturers are following suit.

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