Part load operating point for a controlled auto-ignition four-stroke internal combustion engine is reduced without compromising combustion stability through load dependent valve controls and fueling strategies. Optimal fuel economy is achieved by employing negative valve overlap to trap and re-compress combusted gases below a predetermined engine load and employing exhaust gas re-breathing above the predetermined engine load. Split-injection fuel controls are implemented during low and intermediate part load operation whereas a single-injection fuel control is implemented during high part load operation. Split-injections are characterized by lean fuel/air ratios and single-injections are characterized by either lean or stoichiometric fuel/air ratios. Controlled autoignition is thereby enabled through an extended range of engine loads while maintaining acceptable combustion stability and emissions at optimal fuel economy.