Injector line heaters are a relatively new concept in heating Vegoil
(VO) for better combustion and slight increase in fuel economy and power.

The main goal of most of the components in a VO conversion is to raise
the temperature of the VO prior to injection in the combustion chamber
in order to lower the viscosity of the VO to as close as possibly
equal the viscosity of diesel fuel. Depending on the variety of oil
this occurs at a temperature range of 200°F to 320°F.

Injector line heaters specifically heat the fuel supply lines that run from the IP  to each injector in traditional diesel engines. Recent newer diesel
engine designs have eliminated injector lines to various degrees so
injector line heaters may be of limited usefulness in these. But in
diesel engines with exposed injector lines there exists the
opportunity to add heat to the VO in a range not possible with heat
sources located in the fuel flow prior to the Injector Pump (IP).

The first commercially available injector line heaters were simply  Ni-Chrome wires covered with a fiberglass insulative tube and secured to the injector
lines with high temp aluminum or silicone tapes.

More sophisticated and efficient line heaters are currently being fitted to large truck fleets which have converted to VO. These are available in limited quantities to the public as well. These are engineered to be installed immediately next to the injectors for maximum efficiency and have a high temp adhesive to ensure the best possible heat exchange to the fuel in the injector lines. They also have a insulative and reflective covering on their exterior which helps direct heat to the injector lines and limit heat loss to the surrounding air. A layer of high temp silicone tape acts as additional insulation and on the most sophisticated installations PTFE or silicone high temp insulative sheaths are installed over the injector line heaters as well.
 
Both designs work on the same principal of transferring the heat
generated by electrical resistance to the metal fuel supply lines via
conduction. This heat is then transferred to the VO fuel passing
through the injector lines on its' way to the injectors.

The basic wiring harness for hooking up ILHs looks like: