still new to owning a diesel, please bear with me. i just read the thread about increase mileage by installing fans on the fuel return lines. could someone please explain to me, how much fuel returns to the tank, what is the process of fuel leaving the tank and how is not all used up by the motor. i never realized fuel return to the tank, i assumed once it left the tank, it was used by motor. i am learning more every day off site.

thanks:confused:

The fuel pump pulls fuel from the tank (obviously) into the fuel rail, which feeds the injectors. The pressurized side runs at upwards of 20,000 psi to pop the injectors. Under that much pressure, the fuel can easily reach 100+ degrees F. Unused fuel, and there's a lot of it, is returned to the tank through a fuel cooler. This looks like a transmission cooler, and is mounted between the frame rails, under your truck, in front of the fuel tank. People mount electric fans to the cooler to help cool the fuel down even more. Cool fuel makes horsepower.