Return oil at 88 °C on a 24 V telehandler that has been cycling a 90 L/min pump all afternoon is already cooking the fluid and the seals. That is the duty we size against, not a brochure picture of a clean matrix on a bench. A compact DC oil cooler only earns its keep if the heat leaving the oil matches the heat the fan can dump into the air that actually reaches the core. Miss either side and the circuit keeps climbing. The rest of this note is how we put that cooler on a mo
