S55-equipped cars are incredibly well engineered from a cooling standpoint. The excellent ducting, core design, robust fans, and other factors all play into how well a cooling system works; there are ultimately two factors that cannot be sidestepped—you must have enough heat exchanger surface area, and you must have enough heat exchangers. Even in a road course environment with extremely high ambient temperatures, the S55 engine operates beautifully, with consistent oil and water temperatures.
These constraints have left the S55 with a “fatal flaw”—the engine’s oil cooler is precariously exposed. A direct impact on the oil cooler can have catastrophic effects, draining the S55 of all of its oil in seconds, a dire fate that several owners have experienced in a painfully direct way. CR Racing has since then developed a strong oil cooler guard, specifically designed to shield the S55’s oil cooler from large road debris and prevent much more costly damage.
For the best real-world protection, the S55 oil cooler guard is constructed from a thick stainless steel plate and fastens directly to existing frame members to help spread the impact load across solid structural components. As an acknowledgment of BMW M’s airflow engineering as mentioned above, meticulous consideration was taken to ensure that the opening in the oil cooler guard matched the shape and size of the existing BMW oil cooler air outlet.