Limited technical studies to speciate particulate matter (PM) emissions from gasoline fueled vehicles have indicated that the lubricating oil may play an important role. It is unclear, however, how this contribution changes with the condition of the lubricant over time. In this study, we hypothesize that the mileage accumulated on the lubricant will affect PM emissions, with a goal of identifying the point of lubricant mileage at which PM emissions are minimized or at least stabilized relative to fresh lubricant.
This program tested two low-mileage Tier 2 gasoline vehicles at multiple lubricant mileage intervals ranging from zero to 5000 miles. The LA92 cycle was used for emissions testing. Non-oxygenated certification fuel and splash blended 10% and 20% ethanol blends were used as test fuels. Results collected indicate that both the magnitude and variability of PM mass emissions decrease in the first 2000 miles of lubricant break-in, with potential increases as lubricant ages and decreases its performance activity. Fuel dilution of the lubricant with ethanol does not appear to deteriorate lubricant quality beyond expectations based on mileage alone.
