The Effect of Passenger Car Motor Oil Detergent System on Vehicle Tailpipe Emissions

The International Lubricant Standardization and Approval Committee (ILSAC) GF-2 specification requires Passenger Car Motor oils to provide enhanced fuel economy in a modern low friction engine (ASTM Sequence VIA). The durability of this fuel economy improvement is becoming increasingly important and will be address in the successor to the Sequence VIA, the Sequence VIB, which is currently under development for ILSAC GF-3. Previous investigations have indicated that the choice of detergent system and friction modifier has a large impact on the fuel economy of a lubricant. As a result of a study undertaken to further investigate these effects in a 1994 Ford Crown Victoria running the EPA Federal Test Procedure, a significant impact on tailpipe emissions was discovered. Detergent system affected both regulated emissions (hydrocarbon (HC), carbon monoxide (CO), and oxides of nitrogen (NO_x) emissions), and non-regulated emissions (carbon dioxide emissions). Interestingly, several of the more fuel efficient oils in the study negatively influenced one or more of the regulated emissions while making gains predominantly in the reduction of carbon dioxide. These detergent effects will be discussed for cold transient, stabilized phase, and hot transient emissions, as well as composite and highway emissions. A trend toward increased regulated emissions observed for the baseline oil used in the procedure (Sequence VIA Baseline Calibration Oil, batch 2 (BC-2)) will also be discussed.