What are the advantages of a low W value in a 15W40 multigrade oil?

A low W (winter) value in a 15W40 multigrade oil indicates better performance in colder temperatures, allowing for easier engine starts and improved lubrication during cold starts. This ensures that the oil flows quickly to key engine components, reducing wear and tear. Additionally, a lower W value can enhance fuel efficiency and reduce emissions in colder conditions, benefiting both engine longevity and environmental impact.