LSPI Durability, a Study of LSPI over the Life of a Vehicle

Increasingly stringent emissions standards and the related efforts to increase vehicle fuel economy have forced the development and implementation of many new technologies. In the light-duty, passenger vehicle segment, one key strategy has been downsized, down-sped, boosted engines. Gasoline direct injection, coupled with turbocharging, have allowed for a drastic reduction in engine size while maintaining or improving engine performance. However, obtaining more power from a smaller engine has produced some consequences. One major consequence is the uncontrolled combustion known as Low Speed Pre-Ignition (LSPI). LSPI and the high energy knocking event which frequently follows have been known to result in fractured pistons and catastrophic engine failure. The propensity at which LSPI occurs has been linked to engine oil formulation. The frequency and severity of the LSPI problem has become such an issue that the oil industry, research organizations, and OEMs have developed specialized engine tests to quantify a particular engine oil’s LSPI propensity. Data generated in these tests have increased the industry’s overall knowledge of the LSPI phenomenon and provided a way to develop lubricants that reduce the occurrence of LSPI. However, there are still many questions left unanswered. One important question that the standardized tests do not address is the impact of oil age on LSPI. In this work, the impact of both oil age and engine age on LSPI is investigated. The investigation includes a combination of engine dynamometer testing and LSPI monitoring while a vehicle is operated on public roads, using standard pump gasoline. Data from these two sources shows that both oil age and engine age do influence LSPI propensity. Additionally, data definitively shows that LSPI does indeed occur in the field.