Oil Dilution of a Passenger Car Diesel Engine in Operation with blended Diesel Fuel B10

Currently Biodiesel (RME) is mixed according to EN 14214 and EN 590 with up to 5% of fossil Diesel fuel. With a further increase of RME fraction to 10% (B10 blend), there are uncertainties regarding the undisturbed longlife behavior due to variations of the physicochemical properties of RME in comparison to commercial Diesel fuel.

It is known that an irreversible oil dilution appears in the engine lubrication system as a result of regeneration mode of current passenger car Diesel engines with particulate filters. The cause of these is the higher distillation characteristic of RME in contrast to the fossil Diesel fuel. If unburnt fuel reaches the lubricant in the oil sump via the piston-cylinder assembly during the regeneration of the particulate filter, the RME fraction cannot evaporate from the engine oil due to its distillation characteristic (boiling point > 340 °C) [1]. As a consequence of the oil dilution, an irreversible decrease of the viscosity results with the risk of increasing wear.

The engine bench tests carried out in this project should clarify whether the share of the RME fraction in the engine oil of a passenger car diesel engine equipped with a particulate filter and operated with B10 blend is higher than the share of the Diesel fuel fraction. The Fachagentur Nachwachsende Rohstoffe e.V. (FNR) and the Union zur Förderung von Oel- und Proteinpflanzen e.V. (UFOP) financed this project. It was supported by Volkswagen AG Wolfsburg with the provision of the diesel engine and by Fuchs Europe Schmierstoffe GmbH Mannheim, which provided and analyzed the engine oil.