Anybody can make biodiesel. It's easy, you can make it in your kitchen -- and it's BETTER than the petro-diesel fuel the big oil companies sell you. Your diesel motor will run better and last longer on your home-made fuel, and it's much cleaner -- better for the environment and better for health.
If you make it from used cooking oil it's not only cheap but you'll be recycling a troublesome waste product. Best of all is the GREAT feeling of freedom, independence and empowerment it will give you. Here's how to do it -- everything you need to know.
There are at least three ways to run a diesel engine on biofuel using vegetable oils, animal fats or both. All three are used with both fresh and used oils.
1. Use the oil just as it is -- usually called SVO fuel (straight vegetable oil);
2. Mix it with kerosene (paraffin) or petroleum diesel fuel, or with biodiesel, or blend it with a solvent, or with gasoline;
3. Convert it to biodiesel.
The first two methods sound easiest, but, as so often in life, it's not quite that simple.
1. Mixing it
Vegetable oil is much more viscous (thicker) than either petro-diesel or biodiesel. The purpose of mixing it or blending it with other fuels is to lower the viscosity to make it thinner so that it flows more freely through the fuel system into the combustion chamber.
If you're mixing veg-oil with petroleum diesel or kerosene (same as #1 diesel) you're still using fossilfuel -- cleaner than most, but still not clean enough, many would say. Still, for every gallon of
vegetable oil you use, that's one gallon of fossil-fuel saved, and that much less climate-changing carbon in the atmosphere.
People use various mixes, ranging from 10% vegetable oil and 90% petro-diesel to 90% vegetable oil and 10% petro-diesel. Some people just use it that way, start up and go, without pre-heating it (which makes veg-oil much thinner), or even use pure vegetable oil without pre-heating it, which would make it much thinner.
You might get away with it with an older Mercedes 5-cylinder IDI diesel, which is a very tough and tolerant motor -- it won't like it but you probably won't kill it. Otherwise, it's not wise.
To do it properly you'll need what amounts to an SVO system with fuel pre-heating anyway, preferably using pure petro-diesel or biodiesel for starts and stops. (See next.) In which case there's no need for the mixes.
Blends with various solvents and/or with unleaded gasoline are "experimental at best", little or nothing is known about their effects on the combustion characteristics of the fuel or their long-term effects on the engine.
Higher viscosity is not the only problem with using vegetable oil as fuel. Veg-oil has different chemical properties and combustion characteristics from the petroleum diesel fuel for which diesel engines and their fuel systems are designed.
Diesel engines are high-tech machines with very precise fuel requirements, especially the more modern, cleaner-burning diesels (see TheTDI-SVO controversy).
They're tough but they'll only take so much abuse. There's no guarantee of it, but using a blend of up to 20% veg-oil of good quality is said to be safe enough for older diesels, especially in summer.
Otherwise using veg-oil fuel needs either a professional SVO solution or biodiesel. Mixes and blends are generally a poor compromise. But mixes do have an advantage in cold weather.
As with biodiesel, some kerosene or winterised petro-diesel fuel mixed with straight vegetable oil lowers the temperature at which it starts to gel. (See Using biodiesel in winter) More about fuel mixing and blends.