What is the difference between Mobil Super 5w30 and 5w40?

[JuniperAnn]

The differences between Mobil Super 5w30 and 5w40 are: 1. Different high-temperature viscosity: 5w30 has lower high-temperature viscosity, better fluidity, and faster engine heat dissipation; 5w40 has higher high-temperature viscosity, poorer fluidity, but less fluctuation and greater stability. 2. Different applicable objects: 5w30 can effectively reduce fuel consumption and has lower noise, making it suitable for new cars or naturally aspirated engines; 5w40 has higher viscosity and is more suitable for older cars. The number after 'W' in the oil model indicates the kinematic viscosity of the engine oil at 100 degrees Celsius. The larger the number, the higher the viscosity, meaning better and more stable protection at high temperatures, with a lower possibility of thinning at high temperatures.

[LaReed]

Mobil Super 5w30 and 5w40 mainly differ in viscosity. The number 5w represents low-temperature performance, ensuring smoother starts in cold weather, with smaller numbers indicating faster flow. The numbers 30 and 40 indicate viscosity at high temperatures; 30 is thinner, which can help save fuel and is suitable for daily city driving in newer cars. 40 is much thicker, especially beneficial for highway driving in hot weather, providing better protection for older engines and reducing wear. I've tried driving on mountain roads in hot summer with 40 oil, and the engine was noticeably quieter with less vibration. Most newer car models recommend 30 oil because their engines are more advanced and don’t need such thick oil. However, if your car manual specifies 40, don’t switch to 30 arbitrarily, as it may lead to unstable oil pressure and shorten engine life. In short, choose based on the season and your car type for the best results.

[OEmily]

When choosing car engine oil, I prioritize whether it matches my driving habits. Both 5w30 and 5w40 are designed for different temperatures. They perform similarly in low temperatures, making cold starts easier, but the difference is significant in summer heat: 30 is thinner, offers better fuel efficiency, and feels more responsive during acceleration; 40 is thicker, providing an extra protective layer for the engine, especially beneficial for long-distance driving or heavy loads. I've used 30 oil for years, saving on fuel costs for city commutes and enjoying longer oil change intervals. However, during a trip to a hot region, I noticed engine overheating and later learned that switching to 40 is recommended in hotter weather. Newer cars generally use 30, while older vehicles or those frequently driven at high speeds should use 40—don’t overlook the car’s age. Also, stick to the same brand to avoid mixing oil types, which could cause reactions and potential issues.

[AveryAnn]

Simply put, the main difference between Mobil Super 5w30 and 5w40 lies in the second number: 30 indicates lower viscosity, allowing faster engine operation in summer, making it suitable for new cars with better fuel efficiency; while 40 has higher viscosity, providing stronger resistance at high temperatures and preventing wear in older vehicles. The difference in winter startup is minimal. I've noticed new car owners prefer 30 because it's quieter and more fuel-efficient, while experienced drivers choose 40 for added protection. Always follow your vehicle's manual—don't switch randomly, as using the wrong oil accelerates engine aging. Change oil regularly and check every few thousand kilometers to prevent minor issues from escalating.