The reason is that it is an integral component in the radiator cooling circuit, which is normally not used in medium-sized cars. Only very strong engines are equipped with additional oil radiators. That’s why we find them exclusively in the sports and luxury sports cars. Normally, the engine oil is cooled only when it is in the oil sump, located at the bottom of the vehicle where it is in constant contact with the wind. The cooling method here is identical to that of the radiator.
Once the cup is reached, the engine oil may expand and lose part of its pressure, which would result in a decrease in temperature. Despite being a few degrees Celsius, this decline is more than enough. The oil radiator has a back-up function and is surrounded by the same coolant that we find in the regular radiator. The fan and the wind passing through the radiator grid are still more than sufficient in this case. In either case, sufficient amount of oil must be inside the circuit. To assure you, use the oil dipstick. Along with the level, also check the oil color, as this can determine the state of the oil filter. In the most performing cars, some manufacturers install additional oil temperature sensors that, most often, only detect oil temperature sensor data.
Because the oil is the coolant used the same circuit, both heat up or cool down at the same time. The oil spill case would also be useful to check the condition of the oil cooler. Regardless of the brand you are interested in, you will find excellent spare parts (eg Parktronic, wheel hub, pulley, direction indicators, spoilers, etc.) at a very advantageous price.