Advanced combustion engines have the potential to simultaneously increase efficiency and reduce criteria pollutants. Low NOx emissions are achieved by avoiding near stoichiometric regions or by using high levels of dilution and low soot emissions are achieved by using high levels of pre-combustion mixing. Efficiency is increased by reducing heat transfer losses using dilute combustion and shortening the burn duration through advanced ignition concepts. Examples of advanced combustion modes include lean burn gasoline direct injection, gasoline compression ignition (GCI), homogenous charge compression ignition (HCCI), reactivity controlled compression ignition (RCCI), diesel low temperature combustion (LTC), and others.