Shell Mysella S3 S is a high performance quality oil blended for use in 4-stroke, spark-ignition engines which require a 'medium ash' oil or use sour gases such as landfill, bio or sewage gas as fuel. Shell Mysella S3 S is also suitable for engines that traditionally require a medium ash oil to protect the valve seating area of the cylinder head. Shell Mysella S3 S satisfies the new generation of stationary gas engines designed to meet the emerging legislation limiting emissions of NOx, and those which employ the latest 'lean' or 'clean' burn technology.