The choice of oil viscosity, such as 20W50 or 10W50, can depend on various factors, including climate conditions and the manufacturer's recommendations. The oil viscosity rating consists of two numbers, with the first number indicating the oil's viscosity at lower temperatures and the second number indicating its viscosity at higher temperatures.
In general, a lower first number (e.g., 10W) indicates better cold-start performance, allowing the oil to flow more easily during colder conditions. A higher second number (e.g., 50) indicates a thicker oil that maintains its viscosity better under high temperatures and heavy loads.
The Duke 390 is a high-performance motorcycle, and the manufacturer's recommended oil viscosity is typically designed to meet the specific requirements of the engine, considering factors such as engine design, clearances, and operating conditions. It's generally advisable to follow the manufacturer's recommendations to ensure optimal performance and longevity of your bike's engine.
While the Motul 7100 20W50 oil may still provide adequate lubrication and protection, using an oil viscosity that deviates significantly from the manufacturer's recommendations could potentially affect engine performance or even void warranty coverage. If the service centers insist on 10W50 oil, it's worth considering their advice, as they likely have experience with the specific model and have seen the best results with that viscosity.
If you have concerns or want to explore alternative oil options, it's recommended to reach out to a KTM service center or contact KTM customer support directly for the most accurate and up-to-date information regarding the appropriate oil for your Duke 390.