10W-40 vs 10W-50 vs 10W-60: Which Oil is Right for You?

What Do Those Numbers Mean?

The first number (10W) is the oil's viscosity at cold temperatures (the "W" stands for Winter). The second number (40, 50, or 60) is the viscosity at operating temperature (212°F / 100°C).

10W-40: The All-Around Choice

Best for: Normal riding conditions, moderate climates, stock engines

AMSOIL 10W-40 Synthetic Dirt Bike Oil is the most popular choice. It provides excellent protection for most riding conditions while maintaining good fuel efficiency and easy cold starting.

• ✅ Great for trail riding
• ✅ Good cold-weather starting
• ✅ Suitable for most stock engines
• ✅ Balanced protection and efficiency

10W-50: Hot Weather & Hard Use

Best for: Hot climates, desert riding, modified engines, hard racing

AMSOIL 10W-50 maintains thicker film strength at high temperatures. If you ride in 90°F+ weather or push your bike hard, this is your oil.

• ✅ Better high-temperature protection
• ✅ Ideal for desert riding
• ✅ Great for modified/high-compression engines
• ✅ Better for sustained high-RPM use

10W-60: Maximum Protection

Best for: Extreme conditions, older engines with wear, European bikes

AMSOIL 10W-60 is the thickest option. It's designed for maximum protection in extreme conditions or for engines with significant wear.

• ✅ Maximum film strength
• ✅ Best for engines with 100+ hours
• ✅ European bikes (KTM, Husqvarna, GasGas)
• ✅ Extreme heat and hard racing

The Bottom Line

Check your owner's manual first. Most Japanese bikes call for 10W-40, while European bikes often specify 10W-50 or 10W-60. When in doubt, start with 10W-40 and adjust based on your riding conditions and climate.