What is one reason rotary gear and vane type primers contain oil?

The presence of oil in rotary gear and vane type primers serves primarily to lubricate and protect the metal components within the pump. Oil acts as a lubricant, reducing friction between moving parts, which is essential for maintaining the efficiency and longevity of the pump. Additionally, the oil provides a barrier against corrosion and wear, which can occur due to exposure to fuel, water, and other contaminants found in pumping environments.

While flow rates, cooling, and fuel efficiency are important factors in pump operation, they are not the primary reasons for including oil in these types of primers. Enhancing flow rates is a function of the pump design and operation rather than the oil content. Cooling is a crucial aspect of maintaining pump temperature, but this is typically managed by the design of the cooling system rather than through the use of oil in the primer. Increasing fuel efficiency pertains more to the operation of engines rather than the lubrication function of oil within the pump. Therefore, the lubrication and protection of metal parts represent the core purpose of oil in rotary gear and vane type primers.