To solve the coolant restriction issue, many companies offer aftermarket coolant filtration devices that mount between the engine and radiator. While these units do in fact remove contaminants from the cooling system, they do not address the corrosion issues common to aluminum heat exchangers and coolant. However, the approach Bulletproof Diesel took is different. Rather than simply filtering contaminants from the coolant, they redesigned the system so that engine coolant and oil circuits are completely separate from one another. The Bulletproof kit utilizes airflow to regulate oil temperature. Shown here, the system features an aluminum air-to-liquid cooler that mounts just behind the grill, in the front of the vehicle. The secondary benefit of this system is that it eliminates the often-troublesome OE oil filter and cooler assembly and replaces it with a patented oil transfer block, with a remotely mounted spin-on-style oil filter that offers several benefits over the factory setup. We will discuss these a little later.