Development of a Novel Vehicle-Based Method to Assess the Impact of Lubricant Quality on Passenger Car Energy Efficiency

The traditional vehicle-based approach to measuring the effect of oil-related fuel economy has relied on separate oil-aging and measurement processes where oil-aging takes place using an established driving protocol like the EPA Approved Mileage Accumulation (AMA) Driving Schedule for vehicle aging, then at set mileage intervals fuel economy is assessed using procedures such as the EPA FTP75 and Highway Fuel Economy emission test protocols described in 40 CFR, Parts 86 and 600. These test methods are useful for producing discrete snapshots of fuel economy at set mileage intervals but are unable to provide continuous information about oil-related changes in fuel economy. During the tests, the vehicle's fuel economy is indirectly calculated using a carbon-balance method of the bagged sample of dilute tailpipe emissions that effectively integrates the fuel economy of the vehicle during the sample interval which varies between eight and fifteen minutes. While being well-established and scientifically accepted the emission sampling method provides no information on the continuous process of oil-related fuel economy change with time and limits the ability to investigate transient driving effects on fuel consumption. In this paper the authors address a novel method to simultaneously age engine oils for gasoline-fueled vehicles, and directly assess vehicle fuel consumption using real-world transient driving conditions with high-speed data acquisition. Due to the use of high-speed data acquisition, the resulting large data files yield continuous information about oil durability, engine operation, and oil-related vehicle fuel economy effects. Comprehensive maps of fuel consumption can be derived based on the matrix of operating conditions (acceleration, deceleration, and steady-state cruising) facilitating the development of optimized engine oil formulations. The method yields vehicle make and model-specific information about engine oil effects under all driving scenarios and correlation to EPA window-sticker fuel economy is established.