US Patent 7621252 Method to optimize fuel economy by preventing cylinder deactivation busyness

A method of transitioning an engine to a cylinder deactivation mode may include determining a ratio of time that the engine is operating in the cylinder deactivation mode for an engine operating condition relative to a total time of engine operation in the operating condition, determining a number of transitions from a full cylinder mode to the cylinder deactivation mode during the operating condition, determining a transition modifier based on the ratio and number, and modifying a transition criterion based on the transition modifier.