Mobil Delvac 1™ synthetic engine oils are designed to lubricate and protect modern low-emission diesel engines, including those with Exhaust Gas Recirculation (EGR) and after treatment systems with Diesel Particulate Filters (DPFs) and Diesel Oxidation Catalysts (DOCs).
Exhaust Gas Recirculation (EGR) Engines and their Challenges 
As heavy-duty diesel emissions standards for nitrogen oxides (NOx), solid matter, hydrocarbons, and carbon monoxide become stricter, OEMs have found innovative ways to meet those requirements while still meeting customer needs for power and efficiency. 
In order to lower the level of NOx in the exhaust, OEMs began incorporating exhaust-gas-recirculation (EGR) systems into their new engines' designs. Although each manufacturer’s EGR system is different, in outline, EGR works by recirculating exhaust gas, metered and controlled by the electronic management system, back into the intake system. This increases the challenge for the engine oil due to the need for greater soot, heat, deposit and corrosion control.