Using a slightly different oil grade, such as SAE 20W-50 instead of the recommended SAE 10W-40, may not cause immediate damage to your motorcycle's engine. However, it's generally recommended to use the oil grade specified by the manufacturer for optimal performance and protection.
The numbers in the oil viscosity rating represent the oil's flow characteristics at different temperatures. The first number (10W) indicates the oil's viscosity at low temperatures, while the second number (40 or 50) represents its viscosity at high temperatures. In this case, SAE 10W-40 is generally a lighter oil that provides better flow at lower temperatures, which is beneficial for startup and cold weather conditions.
Using a heavier oil like SAE 20W-50 may result in increased viscosity, especially at lower temperatures. This can potentially affect the engine's ability to start smoothly and may lead to increased wear during cold starts. Additionally, the heavier oil may have slightly different lubrication properties compared to the recommended grade, which could impact long-term engine performance and longevity.
If possible, it is generally advisable to switch to the oil grade recommended by the manufacturer for your specific motorcycle model. Following the manufacturer's guidelines ensures that the oil's viscosity and properties are optimized for your engine's design and operating conditions.
If you have concerns or want more specific advice regarding the oil grade for your motorcycle, I recommend consulting with a qualified mechanic or contacting the manufacturer's service center for further guidance. They will be able to provide you with the most accurate information based on your specific motorcycle model and its requirements.