Oil Cooler Replacement

replacement
A person or thing that takes the place of another
the act of furnishing an equivalent person or thing in the place of another; "replacing the star will not be easy"
refilling: filling again by supplying what has been used up
substitution: an event in which one thing is substituted for another; "the replacement of lost blood by a transfusion of donor blood"
The action or process of replacing someone or something

oil cooler
This looks like a small Radiator used to cool off the engine oil or the Automatic transmission fluid. As air passes through the cooler, the temperature of the oil in the cooler is reduced. Some units reduce the temperature of the manual Gearbox and Differential lubricants in racing cars.
A heat exchanger for cooling oil. Most automatic transmissions are equipped with an oil cooler that's located inside the radiator. Since the radiator usually runs close to 200 degrees, the amount of "cooling" this kind of setup provides is questionable.