I started a thread similar to this one a while back.
http://ecomodder.com/forum/showthrea...fuel-3773.html
I have been doing a lot of reading lately concerning heating fuel as it applies to non-gasoline systems - ethanol, biodiesel, and veggie oil.
It appears that there is little benefit to heating gasoline.
However, you almost HAVE to heat biodiesel in the winter, just to get it to flow. Vegetable oil is usually heated with engine coolant, but it's best to NOT do it in the tank, as that can cause some premature degradation of the fuel.
The most interesting one though, is ethanol!
It appears that heating ethanol can greatly improve fuel economy!