Castrol criteria for oil selection: we would always recommend you use an oil specifically designed for the vehicle it is needed for. Trizone technology™ guarantees oils that are designed for motorcycles and tested on a motorcycle’s engine, wet clutch and gears.
We would suggest not to use a car oil in a motorbike, even if it has a dry clutch; however an exception to this would be bikes with big capacity engines and small specific output, a dry clutch and a separate gearbox.
Scooters need a specific oil due to the unique way they are built. They require an oil giving very low friction (Jaso MB) and high resistance to heat that works with the continuous variable transmission to protect the low volume engine (typical sump size in a scooter is < 1lt). Castrol’s Scootek technology guarantees all that.
Constructors tend to recommend oils based on their viscosity, API/ Jaso level and its technology (synthetic, part synthetic or mineral), the table below enables you to select oils according to these criteria. At Castrol, we prefer to recommend an oil that is tailored to the usage that owners make of their bikes, whether its city driving or sportive riding or a track day.
You can also use very low viscosity oil for track use. (unless you have an engine with desmodromic distribution, or an old engine that is heavily tuned in which case a higher viscosity would work better).
Most racing teams use ultra low viscosity oils: it is so expensive to get 2 extra horsepower, why waste 5 or more with a high viscosity oil? Want to see dyno test results of Superbike engines with different viscosity oils? We may be tempted to share those with you very soon!