ISO 8217:2012 specifies the requirements for petroleum fuels for use in marine diesel engines and boilers, prior to appropriate treatment before use. The specifications for fuels in ISO 8217:2012 can also be applicable to fuels for stationary diesel engines of the same or similar make and type as those used for marine purposes. ISO 8217:2012 specifies four categories of distillate fuel, one of which is for diesel engines for emergency purposes. It also specifies six categories of residual fuel.