Using 20W40 instead of 20W50 oil in a Bajaj Pulsar 200NS should generally be fine, but it's important to note that it may affect the performance and protection of the engine to some extent. Here's what you need to consider:
Viscosity: The numbers "20W40" and "20W50" represent the viscosity rating of the oil. The first number (20W) indicates the oil's viscosity at colder temperatures, while the second number (40 or 50) represents the viscosity at higher temperatures. In this case, 20W40 has a lower viscosity at higher temperatures compared to 20W50.
Manufacturer's Recommendation: Bajaj typically recommends using the specified grade of oil for their motorcycles. It's advisable to refer to the owner's manual or consult with a Bajaj authorized service center to know the recommended oil viscosity for your specific model, in this case, the Pulsar 200NS.
Engine Performance and Protection: Using a different viscosity oil might affect the engine's performance and protection characteristics. Thicker oil, like 20W50, may provide better lubrication and heat resistance, particularly in hotter climates or during sustained high-speed riding. Thinner oil, like 20W40, may offer easier cold starts and slightly improved fuel economy, but it may not provide the same level of protection under extreme conditions.
Environmental Factors: The choice between 20W40 and 20W50 can also depend on the climate in your area. If you live in a region with high ambient temperatures, using a slightly thicker oil like 20W50 may be beneficial for maintaining proper engine protection and lubrication.
In any case, if you have already used 20W40 oil instead of 20W50, it's generally not a cause for immediate concern. However, it's advisable to switch to the recommended oil grade at the next oil change to ensure optimal engine performance and longevity. If you have any doubts or concerns, it's always best to consult with a Bajaj authorized service center or a qualified mechanic for personalized advice based on your specific circumstances.