On those engines having direct fuel injection to each cylinder allow an economy mode for 6 cylinder vehicles to reduce to 4 cylinders, 8 cilnders to reduce to 6 or 4. The cylinders would stay out unless load demanded more power. This would increase highway MPG significantly. I'm sure this is already being done on some vehicles but not all.
Dave Bristel 08/23/2011
To avoid problems due to some cylinders not being used for extended times, you would want a system that alternates which cylinders are active, so while it might go from 8 to 6 to 4 cylinders, which cylinders are being used should alternate. I agree that this WOULD help in many situations, but keep in mind that a larger engine will still be heavier than a smaller engine, and that will mean a lower fuel economy vs. a smaller engine.
Brian Langston 07/04/2011
Several car companies have engines that can do this, but none of the Fords.