What the meanig of «EGR (Exhaust Gas Recirculation)»?
EGR (Exhaust Gas Recirculation) systems are installed on vehicle engines only for environmental reasons and to reduce harmful nitrogen oxide emissions, because the most toxic components of vehicle exhaust gases are hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx).
High combustion temperatures of the fuel-air mix are the reason for the significant amount of nitrogen oxides in the exhaust gases. The function of EGR is to feed some of the exhaust gases from the exhaust manifold into the intake manifold at certain engine operating conditions. Feeding the exhaust back into the combustion chamber for recombustion displaces oxygen, which in turn creates a cooler combustion of the fuel-air mixture. Thus, a lower combustion temperature of the fuel-air mixture contributes to a lower formation of nitrogen oxides (up to 30%), which, in its turn, improves the environmental parameters of the engine. The main component of the recirculation system is the EGR valve, which, in fact, ensures that a certain portion of the exhaust gases from the exhaust manifold flows into the intake manifold.
Mainly the diesel engines of trucks are equipped with EGR systems. Apart from the reduced emission of nitrogen oxides it allows the smoother and softer running of the engine, as well as an improvement in some of the operating properties.
At the same time, exhaust gas recirculation has a negative effect on the engine oil, which can lead to a reduction in engine life or engine failure. Oils used for lubrication of engines equipped with EGR exhibit increased soot content, acid number and viscosity.
The API CI-4 specification was developed to prevent performance degradation because of EGR. Oils that meet the API CI-4 requirements have improved properties compared to previous specifications. They have been specifically tested in recirculating engines to withstand severe sooting, resist rising acid numbers, and retain their viscosity grade throughout the service interval.
The oils with European classification ACEA E7 are close to API CI-4. Motor oils that meet or exceed the requirements of API CI-4, ACEA E7 (API CJ-4/CK-4 and/or ACEA E4/E6/E8/E9/E11) are fully suitable for use in trucks equipped with EGR systems and maintain their durable and reliable operation.