What is the difference between 5w40 and 10w40 motorcycle engine oil?

[StRemington]

Motorcycle engine oil 5w40 and 10w40 have the following specific differences: 1. Maximum ambient temperature they can adapt to: The number 40 represents viscosity, and the larger the number, the higher the viscosity and the higher the maximum applicable temperature. Both 5w40 and 10w40 oils can adapt to the same maximum ambient temperature. Additionally, higher viscosity oils may be more suitable for high-speed driving or heavy-duty vehicles. 2. Minimum temperature they can withstand: The smaller the number before W, the lower the low-temperature viscosity and the better the low-temperature fluidity, meaning the lower the minimum applicable temperature. Therefore, compared to 10w40, 5w40 oil can adapt to lower minimum temperatures. Oils with lower numbers before W can start the engine more easily in cold weather.

[TessaFitz]

I used to ride motorcycles during winter in the north. 5W40 oil maintained good fluidity even at -20°C, making engine starts noticeably smoother. In contrast, 10W40 oil thickened at -15°C, resulting in much harder cold starts. When summer temperatures rose, the high-temperature viscosity protection of both 40-grade oils was similar. The main difference lies in winter fluidity, where 5W40 offers significantly better low-temperature start protection. Choosing engine oil requires considering seasons and regions - 5W40 is more worry-free in the north, while 10W40 can be used year-round in the south. However, don't blindly change viscosity grades; always check the manual's recommendations first, especially for older vehicles that may only suit 10W40. Cold start wear causes the most engine damage, making good low-temperature fluidity absolutely critical.

[DeMarcus]

The number before the W in the oil grade represents the low-temperature viscosity. The smaller the number, the better the low-temperature fluidity. 5W40 has stronger low-temperature performance than 10W40, functioning normally at -30°C, while 10W40 reaches its limit at -25°C. Both have the same high-temperature viscosity of 40, offering similar engine protection under high temperatures. During cold starts, 5W40 can lubricate critical parts faster, which is particularly important for engine protection. Using 10W40 in winter may cause difficulty in ignition and increase the risk of engine wear. It's best to choose oil based on regional climate: 5W series for cold regions, while 10W is sufficient for tropical areas. Always use motorcycle-specific oil when changing oil, and avoid substituting with car oil.

[DiJoseph]

I feel that using 5W40 makes the engine start faster, and it fires up immediately in winter; with 10W40, the engine sounds noticeably more strained in cold weather. This is especially obvious in regions with large temperature differences: below zero degrees, 5W40 flows quickly and provides sufficient protection, while 10W40 always requires half a minute of warm-up. In summer under high temperatures, the lubrication effects of both are basically the same, since the '40' viscosity is identical. Using the wrong oil for a long time may affect engine lifespan, especially for older motorcycles. Now, I pay attention to the oil grade every season, switching to 5W40 in winter and 10W40 in summer, which both protects the vehicle and avoids waste. Remember, always choose the viscosity range specified in the manufacturer's manual—it's the safest bet.