Here is how one company explains liquid vs air cooled ZTR's. Do you agree? What are the advantages of liquid-cooled engines vs. air-cooled engines? Generally speaking, it is said that a liquid-cooled engine "may" last up to 50% longer than comparable air-cooled engines due to a constant, correct operating temperature. Engine oil viscosity does not break down as quickly due to the more stable temperature ranges at which liquid-cooled engines run. Liquid-cooled engines experience increased fuel economy compared to standard air-cooled models due to the more consistent operating engine temperatures. A properly designed system keeps the radiator out of harms way (debris, branches, etc) and the cooling fan draws hot air through the radiator, past the engine and away from the operator. This results in a cooler engine and a cooler operator. Liquid-cooled engines are slightly more “forgiving” if the exterior of the engine is not kept clean, unlike air-cooled engines that rely upon heat dissipation for proper cooling. There is little extra maintenance involved with a liquid-cooled engine versus an air-cooled. Keeping the radiator clean is the biggest factor. However, this is simple to do by using the removable screen that can be removed and tapped clean in the field, with no tools required. The major benefit of an air-cooled engine is that they are simpler in design as they have fewer parts involved. Because of this, they are less expensive in price and potential repair cost.