[Christ]

The grid heater is designed to bring the air temperature up during cold starts for diesel engines. You probably knew that.

The problem is that it's a resistive element heater, and is going to draw ALOT of juice from your electrical system. It's almost never going to be profitable to introduce another waste stream into your engine's systems to gain any kind of efficiency, because it will be a net loss.

Frankly, unless you need cold start assistance (not likely unless you have serious engine problems) I wouldn't really bother.