What component maintains an even temperature of oil in the engine crankcase through water circulation?

The component that maintains an even temperature of oil in the engine crankcase through water circulation is the oil cooler. Oil coolers are specifically designed to reduce the temperature of engine oil, which is essential for optimal engine performance and longevity. By circulating water (coolant) through the oil cooler, heat is transferred from the hotter oil to the cooler water, thereby lowering the oil's temperature and preventing it from overheating. This process ensures the oil remains at an effective viscosity for proper lubrication, allowing for smooth engine operation.

While heat exchangers might seem relevant, they refer to any system that transfers heat between two fluids and could include several types of systems, not exclusively for oil cooling. Radiator coolers are typically used in the context of cooling engine coolant rather than oil. Thermal insulators, on the other hand, serve to retain heat rather than dissipate it. Thus, the primary function of an oil cooler is the direct and effective regulation of engine oil temperature, making it the correct choice for this question.