The Webasto Thermo Top C coolant heater provides 17,000 Btu/h of heat to bring the engine up to operating temperature quickly, so it's running efficiently. This helps fleets to save fuel, reduce engine wear, maintenance costs and exhaust emissions by not idling. The Thermo Top C uses as little as 1 gallon of fuel in a 10-hour period. This product is a CARB-approved and EPA SmartWay Verified Technology.