Experimental Evaluation of the Fuel Consumption and Emissions Reduction Potential of Low Viscosity Lubricants

Reducing fuel consumption and emissions from road transport is a key factor for tackling global warming, promoting energy security and sustaining a clean environment. Several technical measures have been proposed in this aspect amongst which the application of low viscosity engine lubricants. Low viscosity lubricants are considered to be an interesting option for reducing fuel consumption (and CO₂ emissions) throughout the fleet in a relatively cost effective way. However limited data are available regarding their actual “real-world” performance with respect to CO₂ and other pollutant emissions. This study attempts to address the issue and to provide experimental data regarding the benefit of low viscosity lubricants on fuel consumption and CO2 emissions over both the type-approval and more realistic driving cycles. In addition, regulated (CO, HC, NOx, PM) and non-regulated (particle number and size distribution) pollutant emissions were monitored and analyzed in order to assess other possible environmental benefits. For the study a Euro 3 and a Euro4 diesel passenger car were employed and a series of measurements were performed using regular service lubricants (15W-40, 10W-40 and 0W-40) and fuel efficient (ACEA B5 grade) low viscosity lubricants (5W-30 and 0W-30). The test sequence included the NEDC and the Artemis driving cycles which are considered to better simulate the urban, rural and motorway driving conditions in Europe. Furthermore, engine test bench measurements were performed on fuel consumption in order to investigate and compare the effect of replacing a mineral with a low viscosity synthetic lubricant over several different engine operating points. Vehicle measurement results indicate that low viscosity lubricants in most cases offer a quantifiable reduction in CO₂ emissions. However, higher reductions were experienced over the less transient NEDC (1.6-3.6%) compared to the Artemis cycles (0.4-1.8%). Test bench results were in-line with those of the vehicles and indicated that there are certain operating points were the lubricant effect is enhanced. Marginal differentiations in pollutant emissions were observed in all cases.