What type of substances are used in the formulation of multigrade oils?

Multigrade oils are designed to function efficiently under a wide range of temperatures. The key to their versatility lies in the use of polymers, which are essential in modifying the viscosity of the oils. These long-chain molecules provide the desired characteristics that ensure the oil remains sufficiently thick at high temperatures while also maintaining fluidity at low temperatures. The polymers create a stable structure that allows the oil to flow easily in colder conditions while protecting engine components at elevated temperatures.

In contrast, emulsifiers, solvents, and surfactants serve different purposes that are not directly related to the formulation of multigrade oils. Emulsifiers typically help to mix two immiscible liquids, solvents act to dissolve other substances, and surfactants lower the surface tension between liquids or between a liquid and a solid. While these substances may play roles in other formulations or applications, they do not provide the necessary viscosity modulation that polymers do, which is critical for the performance of multigrade oils.