Increased soot levels can cause sludge, and clog Exhaust gas recirculation or EGR is a system used to reduce emissions in many new diesel engines. The EGR device redirects some of the exhaust gases normally emitted by the vehicle back into the engine. These gases are cooled and then diverted through the intake manifold into the cylinders along with some filtered and turbocharged air from outside the vehicle. This blend of spent and unspent gases is used in the combustion process, resulting in lower peak-flame temperatures and the creation of fewer Nitrogen Oxides (NOx).