Which of the following is not a use of 2190 oil?

The correct option indicates that cooling engines is not a use of 2190 oil. Marine lubricants like 2190 oil are specifically formulated for lubrication needs, such as for main reduction gears (MRGs), low, medium, and high pressure air compressors, and steam turbines.

In the case of cooling engines, this is not the intended function of 2190 oil. Instead, engines are typically cooled using water or specialized coolant fluids that facilitate the heat exchange process, managing engine temperature effectively. Therefore, while 2190 oil serves critical functions in lubrication, it is not utilized for cooling purposes, making the identification of this specific use correct in the context of the question.