What Is the Purpose of a Fuel Oil Heat Exchanger? The purpose of a fuel oil heat exchanger is twofold: it heats fuel oil to reduce its viscosity so it can be pumped, filtered, and atomized at the burner, and it recovers process heat to improve energy efficiency. Without controlled heating, heavy fuel oil is too thick to handle and burns poorly, so the exchanger is central to both operability and combustion quality. Direct Answer A fuel oil heat exchanger conditions fuel oil