The function of the oil cooler is to lubricate and cool the oil. The location of the oil cooler is near the radiator, and it is to maximize cooling airflow. The reason of exist of oil cooler is in order to maintain the lubricative properties of oil, and the oil has to be cooled down in a proper temperature range. The engine oil works not only in lubrication, but also in cooling since the oil carries away a lot of the heat produced by the engine. We recommend you to change the oil cooler if you drive your BMW over 50,000 miles. Here are some symptoms showing your oil cooler is failing: if the engine power loss owing to oil contamination; if the engine misfires due to oil fouling; if the engine coolant temperature goes up and potential damage due to oil contamination, you should check the oil cooler immediately. We are glad to offer you all BMW genuine OEM oil cooler with a discounted price.