Who is correct regarding viscosity index improvers?

Viscosity index improvers are additives used in engine oils to enhance the viscosity characteristics of the oil across different temperatures. The primary function of these improvers is to ensure that the oil maintains appropriate viscosity levels as temperatures change.

When temperatures rise, the oil naturally tends to thin out. Viscosity index improvers work by increasing the thickness of the oil to counteract this thinning effect, thereby ensuring that the oil retains adequate lubrication properties at elevated temperatures. This is why Technician A's statement is correct—viscosity index improvers thicken the oil when it is hot.

Conversely, at lower temperatures, oil tends to become more viscous or 'thicker.' In this situation, viscosity index improvers help reduce this effect, allowing the oil to flow more freely and providing effective lubrication even in cold conditions. Thus, they thin the oil when it’s cold, but this aspect is not captured accurately by Technician A’s description.

Understanding how viscosity index improvers operate is essential for ensuring optimal engine performance and protection, especially in environments where temperatures fluctuate significantly. This knowledge helps in selecting the right oil for specific operating conditions and extends engine life through improved lubrication.