A method is provided for operating a lean-burn homogeneous charge reciprocating internal combustion engine that includes providing an unthrottled fuel-air compression charge having a lean fuel-air ratio, passing the fuel-air compression charge to fill no more than sixty percent of a cylinder within the internal combustion engine, compressing the fuel-air compression charge within the cylinder, igniting the compressed fuel-air compression charge for combustion, and passing exhaust resulting from the combustion to a NOx removal system. A non-platinum oxidation catalyst may be used to control carbon monoxide emissions in the exhaust Engine power may be varied by controlling the engine speed with a continuously variable transmission, by varying the applied engine load to charge a hybrid system battery, or by varying the amount of the lean fuel-air mixture charged.

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