A distinctive method of operating an internal combustion engine in a low-temperature combustion mode. An engine combustion chamber is provided with fuel and air charges before combustion conditions are reached. The fuel charge is sufficient to provide a fuel-air equivalence ratio of at least 1.05. The fuel and air are allowed to mix prior to combustion. The fuel is provided to the combustion chamber at least 20 crank angle degrees before top dead center. The fuel and air charges are regulated such that the mixture auto-ignites as a result of the heat and pressure generated by the compression stroke. The amounts are further regulated such that combustion occurs below a temperature at which significant soot production occurs. In one embodiment, early intake valve closing is used to limit the air charge. The method provides a rich low temperature combustion mode operation, which has several applications.