What are the differences between 10w40 and 5w40 engine oil?

[LeKeegan]

Engine oil 10w40 and 5w40 have the following differences: 1. 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 applicable minimum temperature. 2. Different environmental temperatures: Compared with 10w40, 5w40 engine oil can adapt to lower minimum temperatures. Engine oil with a lower number before W can start the engine more easily in cold weather. To determine which one is better, it mainly depends on the driving environment of the vehicle. If the environmental temperature is lower, 5w40 is recommended.

[McLuna]

The difference between 10w40 and 5w40 engine oil mainly lies in their performance during cold starts. 5w40 has better low-temperature fluidity, flowing smoothly even at -30°C, making engine ignition and startup easier and more effortless. 10w40 has slightly higher low-temperature viscosity, flowing smoothly only at -25°C, which may result in slightly slower starts in cold weather and increased engine wear. In summer heat, both have the same viscosity of 40, offering similar protective effects, with the engine running smoothly and similar fuel consumption. For everyday drivers, those living in the north should use 5w40 to prevent winter startup issues, while those in the milder south can opt for 10w40, which is more cost-effective. When changing oil, don’t forget to check the vehicle manual for recommendations and avoid mixing different types casually, as this can affect engine longevity and increase repair costs over time. I’ve personally tried two different types and noticed a clear difference.

[SebastianLee]

As someone who repairs cars year-round, distinguishing between oil grades is crucial. The first part '5w' in 5w40 indicates lower viscosity at low temperatures, flowing well at -30°C for smoother engine starts; the '10w' in 10w40 has higher viscosity, struggling to flow at -25°C, making cold starts slightly harder and offering weaker engine protection. The latter number '40' means both have the same viscosity at high temperatures, providing equal protection during summer high-speed driving. Older vehicles are better suited for 10w40 with slightly higher viscosity to reduce wear; new cars benefit from 5w40 for better fuel efficiency. Don’t overlook seasonal changes when changing oil—use 5w40 more in cold northern regions; warmer areas can save money with 10w40. In terms of fuel efficiency, 5w40’s lower resistance might save a bit of fuel, as seen in odometer changes.

[LaPaige]

As a budget-conscious car owner, I prioritize cost-effectiveness when choosing engine oil. 5W40 offers better low-temperature fluidity, making it ideal for cold weather. Although slightly more expensive, it can save fuel due to reduced cold-start resistance and marginally lower fuel consumption. 10W40 has slightly poorer low-temperature viscosity, causing more engine wear during cold starts in sub-zero conditions, but it's cheaper and more economical in warmer regions. At high temperatures, both oils have the same viscosity (40), providing equal protection in summer and similar fuel efficiency. Long-term use of 10W40 in cold climates may increase maintenance costs, but it's fine in warm weather. Choose oil based on local climate—opt for 10W40 if it's not cold; if budget allows, 5W40 offers better engine protection. Make a wallet-friendly decision without waste.