The Development of a Low Viscosity, Highly Efficient Lubricant for Sport Motorcycle Applications

The highly competitive sport motorcycle market demands continuous increase in engine performance. At the same time, legislation in the main industrialized countries establishes stringent limits for gaseous emissions from two wheelers. As already witnessed in the passenger car industry, motorcycle manufacturers are giving increased focus to the lubricant as a potential tool to improve engine performance and reduce gaseous emissions. When compared to a conventional, high viscosity formulation, an optimized low viscosity, low friction engine oil can bring significant increase in power release and fuel economy, as well as a reduction in tailpipe emissions. However, the use of highly efficient lubricants in sport motorcycle applications needs careful evaluation since motorcycle engines with an integrated clutch and gearbox require the lubricant to achieve very precise viscometric and frictional limits. This paper describes the development of a new concept for high performance motorcycle engine oils, capable of delivering a tangible increase in engine efficiency whilst maintaining a high level of wet clutch operability along with good engine and gearbox durability. The development process included the formulation of a specific additive package with an optimized friction coefficient and the definition of a base oil mix with a suitable viscometric profile. A number of candidate formulations were then screened using Castrol's proprietary motorcycle engine test methods for power release and clutch compatibility. A final candidate was field tested for 30,000 km using a high speed track riding cycle. The candidate formulation showed a statistically significant increase in engine power release over a number of high performance engine oils. Wet clutch compatibility and powertrain durability was also equal or better to that obtained with high performance benchmark products.