Many people have a difficult time comprehending why in heck we'd want to put greasy vegetable oil into our perfectly functional diesel vehicles. How could something edible and tasty possibly power a large vehicle? If it works at all, doesn't it take a highly advanced retrofitting of the engine? Believe it or not, vegetable oil is not too far off from what the diesel engine was initially designed to use. Dr. Rudolph Diesel himself designed his engines to run on peanut oil, and introduced them to the world in this manner. He died shortly after the unveiling of his invention (insert conspiracy theory here) and his design was modified to utilize a bi-product of gasoline production, or "diesel fuel." Vegetable oil is combustible and completely functional as a fuel in modern compression ignition engines (Diesel engines) if slight modifications are done to the fuel delivery system. Vegetable oil is inherently sticky or more viscous than diesel fuel and needs to become more fluid in order to properly function in a Diesel engine. How do you thin veggie oil and make it more fluid? The same way you would turn a clump of caramel into a pour able liquid; by heating it! The method we have used is fairly common and requires the addition of a second tank, a solenoid (electrical switch), a few rerouted coolant hoses, and a second filter. The idea is that you start your engine on diesel or biodiesel and run it for a few minutes to generate heat. As the heat gets carried out of the engine, via the coolant system towards the radiator, it takes a newly added detour into the secondary tank, which contains the veggie oil. Inside the secondary tank, this extremely hot coolant fluid travels through a spiraling coil of copper tubing before it exits the tank and returns to the engine to start its loop over again.

These coils radiate heat into the veggie oil making it thin and runny. Thin and runny fuels make Diesel engines happy. Once the veggie oil attains a temperature of about 175º F, it becomes fluid enough to run through your fuel system without sticking and causing problems. A switch is flipped on the dashboard, the solenoid chooses tank 2 instead of tank 1 and the fuel line begins to take in Vegetable Oil. The path from the veggie fuel tank to the engine includes some form of heat transfer. Again, the heat is being transferred from hot engine coolant to the cooler vegetable oil. One commonly used method is the "hose within a hose." Try and picture a thin fuel line filled with vegetable oil, flowing in one direction. Then in your minds eye, add the image of a larger rubber coolant hose surrounding that, filled with coolant flowing in the other direction. The smaller hose of veggie is inside the big hose of coolant (you can see this in the next picture, before the gold filter housing, a small hose comes out of a big hose). In essence, the fuel line is bathed in heat, which diffuses through the hose and into the veggie oil. How you get a hose into another hose without leaking fluid is a simple matter of getting the right fittings.