I purchased a stock Mercedes fuel heater(connects to coolant hose) on eBay and the previous thread on WVO heaters got me wondering about the installation instructions. The instructions say to install the heater in the hose run from the head to the heater core. It states that this is necessary because "In the summer the car heater is usually turned off at temperatures above 70 degrees, stopping the flow of coolant through the fuel heater as well. This prevents the fuel from being overheated, which could otherwise result in a loss of power." I am sure the instructions are intended for vehicles running on regular diesel rather than SWO/WVO or biodiesel. However, I was under the impression that even with diesel # 2 that higher fuel temperatures would result in more complete combustion because of faster ignition and better spray pattern from the lower viscosity. Also, If the fuel was heated by coolant from a system with a working thermostat, how could it get that much hotter in the summer?

Thanks

Sedecrem