Which oil grade offers a wider temperature range for operation?

The choice of SAE 10W-40 as the oil grade that offers a wider temperature range for operation is based on its viscosity characteristics. The 'W' in these oil designations stands for winter, which indicates how the oil behaves at lower temperatures. The number before the 'W' indicates the oil's viscosity in cold conditions, while the number after 'W' indicates its viscosity at high temperatures.

SAE 10W-40 starts with a lower viscosity rating in colder temperatures (10W) but maintains effective performance up to a higher viscosity rating at elevated temperatures (40). This means that the oil can effectively flow in colder conditions and also maintain its viscosity when the engine operates at higher temperatures, making it suitable for a broader range of temperature variability.

In contrast, SAE 10W-30 and SAE 5W-30 cover less of the high-temperature range compared to SAE 10W-40. SAE 30 does not offer the same cold-start performance because it lacks the winter rating and is limited to higher temperatures. Hence, while all the options have their own advantages, SAE 10W-40 stands out for its versatility across different operating environments.