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

[DiLucas]

The difference between 5w40 and 10w40 engine oil lies in their respective low-temperature resistance capabilities: 5w40 can withstand temperatures as low as -30 degrees Celsius, while 10w40 engine oil can endure temperatures down to -25 degrees Celsius. The functions of engine oil are: 1. To alleviate friction and high temperatures; 2. To cool and reduce temperature; 3. To clean and purify; 4. To absorb shocks and cushion impacts; 5. To prevent rust and corrosion. Engine oil, also known as motor lubricant, is composed of base oil and additives. The base oil is the main component of lubricating oil, determining its fundamental properties, while additives can compensate for and improve any shortcomings in the performance of the base oil.

[CamillaDella]

As an average car owner, I've asked mechanics many times during oil changes: the main difference between 5w40 and 10w40 lies in winter performance. The number before the "W" like 5 or 10 indicates better flow at cold temperatures when smaller - 5w40 flows like water even at -30°C, making engine starts easier with less wear on new engines, while 10w40 may thicken slightly at the same low temperature, making engine cranking a bit harder. But in summer heat, their second "40" viscosity rating provides identical engine protection. Having driven in northern regions for years, I noticed my engine made "clanking" noises during cold starts with 10w40 in extreme cold, but switching back to 5w40 brought smoother starts and slightly better fuel economy. Pro tip: always check your vehicle manual for oil recommendations - don't risk major engine issues to save small money.

[McRose]

I'm a car enthusiast who loves studying motor oil details: The numbers in 5w40 and 10w40 represent viscosity grades, where 5 and 10 indicate cold-start performance, and 40 denotes high-temperature protection value. The key lies in low-temperature fluidity: 5w40 flows smoothly even at -30°C, reducing engine wear, while 10w40 can only flow around -25°C, potentially causing slightly slower cold starts. At high temperatures, both perform similarly, maintaining stable lubrication during high engine RPMs. Choose based on local climate: 10w40 is cost-effective in warmer southern regions, but 5w40 is safer in northern or colder winter areas for longer engine life. I've tested different brands and found viscosity affects fuel consumption: oils with better fluidity save about 0.5% fuel during initial startup. Regularly check oil levels during maintenance—don't wait until it hardens to change.

[WillowLynn]

From a practical perspective, I see the difference in engine oil as quite simple: 5W40 flows more smoothly during winter starts, while 10W40 is slightly thicker in cold weather. The smaller number before the "W" (like 5) indicates better low-temperature fluidity; a larger number (like 10) might mean the engine hums a bit more in winter. But in summer heat, both have the same 40 viscosity, offering equal protection. The choice depends on climate and vehicle condition: frigid northern regions must use 5W40 to prevent engine wear; warmer areas can opt for cheaper 10W40. Don't forget oil change intervals—dirty oil magnifies these differences.

[SanAdriel]

When driving, I prioritize fuel efficiency and performance, and the difference in engine oil directly affects these aspects: 5w40 has lower viscosity at low temperatures, resulting in less engine resistance during cold starts, quicker starts, and slightly better fuel economy. 10w40 offers slightly higher resistance during winter starts, potentially increasing fuel consumption by 0.3%. At high temperatures, both provide the same level of protection and do not affect acceleration. Choose based on climate: in snowy regions, I stick with 5w40 for faster engine warm-up and longer engine life; in dry, warm areas, 10w40 is just as good. Additionally, oil quality impacts long-term maintenance: inferior oil causes more noticeable viscosity changes, so make sure to get fresh oil changes at professional shops regularly.