The Mercedes GL350, ML300, ML350, R300, R350 3.0CDi Bluetec 4matic all come equipped with a catalytic converter and a diesel particulate filter (DPF).
The catalytic converter is a device that is designed to convert harmful pollutants in the exhaust gases, such as carbon monoxide, nitrogen oxides, and hydrocarbons, into less harmful substances like carbon dioxide, nitrogen, and water vapor. It uses a combination of heat, a precious metal catalyst (such as platinum, palladium, or rhodium), and a reduction agent (usually oxygen) to perform this conversion.