High lubricant consumption has a negative impact on the environment and on drain intervals. It also reduces the life-time of after-treatment systems by clogging particle filters or poisoning catalysts. Oil consumption rates of modern engines have been significantly reduced during the last decade, but they will still have to be reduced to meet the future Euro 5 European standard (COM(2007)19 final - SEC(2007) 60 and 61 - European Commission proposal for Euro V for passenger cars).
In order to study the impact of lubricants formulation on oil consumption, a new method based on lubricant labeling using new radiotracer compounds, was used on running engines. The radiotracers (derivative organic compounds of germanium-69) used for online oil consumption measurements were adapted in order to simulate the distillation interval of each lubricant. An in-house engine test was performed on a diesel 2.2 L direct injection Common Rail engine. A particle filter is installed in the exhaust line in order to trap residues coming from oil combustion and, in particular, radiotracer residues. A test procedure was specially developed in order to compare the selected lubricants. The very high sensitivity of the radiotracer method allowed shortening significantly engine test durations down to less than two hours, with an excellent repeatability on oil consumption.
The impact of lubricants formulation (base oil, viscosity grades, volatility and additives) on oil consumption has been studied in a very pertinent way. This has allowed a comparison of a wide range of SAE 5W-30 and 5W-40 lubricants on a unique engine, under very similar operating conditions.