Assessment of low viscosity engine oils in terms of fuel consumption and engine wear in heavy duty engines fleet test

As a consequence of the increasingly stringent emissions standards in the world and, on the other hand, the foreseen shortage of fossil fuels, the application of low viscosity engine lubricants (LVO) is considered one of the most cost effective contribution to counteract these challenges. The aim of the test was to verify the potential fuel consumption benefits of using LVO in Heavy Duty Vehicles (HDV) found in literature, mainly obtained in engine bench tests, when they are working on real and “on-road” conditions. Parallel to this study, the performance of low viscosity lubricants regarding to engine wear was assessed, since the use of LVO could imply an increase in engine wear rate. Potential higher wear could result in a life cycle reduction for the internal combustion engines or higher maintenance costs, both nondesired effects. In order to achieve this goal, a sample of 39 urban buses comprising two engine technologies (Diesel and Compressed Natural Gas (CNG)) and four different lubricants were studied over more than 60000 km per vehicle, measuring daily mileage and fuel consumption, and also oil performance was monitored (with 3000 km sampling frequency) using a deep and extensive oil analysis program, specially engine wear was quantified using ICP-OES, in order to detect abnormal engine wear patterns. Results obtained have shown a positive correlation between the use of LVO and fuel consumption reduction in HDV, both for Diesel and CNG. Regarding to oil performance, results indicate that engine wear do not show abnormal patterns due to use of LVO.The authors would like to thank the Spanish Ministerio de Ciencia e Innovación for its funding in this project (Project no. TRA2012-30907), and thank Repsol and EMT de Valencia for their collaboration. Additionally, the authors would like to thank Ruth Calatayud, Lorena Garzón, Leonardo Ramírez and Santiago Ballester for their help in this work