What is the difference between 10w40 and 10w50?
3 Answers
10w40 and 10w50 have the following differences: 1. Different viscosity: 40 represents the viscosity. The larger the number, the higher the viscosity and the higher the maximum applicable temperature. 2. Different vehicle attributes. 3. Different fluidity: The number before W represents the minimum temperature it can withstand. The smaller the number before W, the lower the low-temperature viscosity, the better the low-temperature fluidity, and the lower the minimum applicable temperature. 4. Different environmental temperatures: Compared with 10w50, engine oil 10w40 can adapt to lower minimum temperatures. Engine oil with a lower value before W can start the engine more easily in cold weather.
As an ordinary person who often helps friends choose cars, I've found the biggest difference between 10w40 and 10w50 lies in their high-temperature performance. These two motor oils perform similarly during winter starts, both functioning properly at around -25°C. But the gap becomes apparent during summer highway driving - 10w50 maintains higher viscosity at high temperatures, like putting an extra protective layer on the engine. Last time my friend took his old Tiguan on a long trip, switching to 10w50 noticeably reduced engine noise. However, for daily city driving, 10w40 offers better fluidity and fuel efficiency, especially being more friendly to small-displacement turbocharged engines. It really depends on your driving habits - if you frequently carry heavy loads uphill or have an older vehicle, 50 is recommended, while 40 is sufficient and more economical for regular commuting.
I've been off-roading for ten years and have tried both of these engine oils in different vehicles. The low-temperature performance of 10w40 and 10w50 is indeed the same, both usable at -25°C. However, the high-temperature viscosity index of 50 is much higher. Last summer, I specifically switched to 10w50 when driving my modified Land Cruiser into the desert. Climbing dunes in scorching temperatures over 50°C, the temperature gauge stayed steady—if I had used 40, the alarm might have gone off. But for friends driving urban SUVs in the city, don’t follow my example. 40 is more suitable for daily scenarios, offering quicker starts and lower fuel consumption. If you frequently haul loads on mountain roads or enjoy desert crossings, the oil film strength of 50 is truly impressive.
