Maintaining oil viscosity in the lubrication system is achieved primarily by the oil cooler in what way?

• A. Increase oil filtration efficiency.
• B. Add anti-wear additives.
• C. Increase oil pressure.
• D. Transfer heat from the oil to the cooling medium, preventing overheating and maintaining viscosity.

Answer: (D)

Oil viscosity is highly temperature-dependent: as oil gets hotter, it becomes thinner and its lubricating film can weaken. An oil cooler works by transferring heat from the oil to the cooling medium, preventing overheating. By keeping the oil at the intended temperature, the cooler preserves its viscosity within the required range, ensuring proper film strength and lubrication in the bearings. Other options don’t directly control viscosity—filtration improves cleanliness, additives affect wear protection rather than viscosity, and simply increasing pressure doesn’t maintain the oil’s viscosity.