There are at least 3 ways to run a diesel engine on biofuel using vegetable oils, animal fats or both. All 3 are used with both fresh and used oils.

1. Use the oil simply as it is-- typically 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 gas;

3. Convert it to biodiesel.

The very first 2 methods sound easiest, but, as so typically in life, it's not rather that easy.

1. Mixing it

Vegetable oil is much more thick (thicker) than either petro-diesel or biodiesel. The purpose of mixing it or mixing it with other fuels is to decrease the viscosity to make it thinner so that it streams more easily 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 the majority of, but still not clean enough, numerous would state. Still, for every single gallon of

veggie oil you use, that's one gallon of fossil-fuel saved, and that much less climate-changing carbon in the atmosphere.

People utilize numerous blends, ranging from 10% veggie oil and 90% petro-diesel to 90% vegetable oil and 10% petro-diesel. Some people just use it that method, launch and go, without pre-heating it (which makes veg-oil much thinner), or even utilize pure grease without pre-heating it, which would make it much thinner.

You may get away with it with an older Mercedes 5-cylinder IDI diesel, which is an extremely tough and tolerant motor-- it won't like it but you probably will not eliminate it. Otherwise, it's not wise.

To do it correctly you'll require what totals up 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 requirement for the mixes.

Blends with various solvents and/or with unleaded fuel are "experimental at finest", little or nothing is understood about their impacts on the combustion qualities of the fuel or their long-lasting effects on the engine.

Higher viscosity is not the only problem with using grease 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 modern machines with extremely accurate fuel requirements, especially the more modern, cleaner-burning diesels (see The TDI-SVO debate).

They're tough however they'll only take so much abuse. There's no guarantee of it, however utilizing a blend of up to 20% veg-oil of excellent quality is stated to be safe enough for older diesels, particularly in summer season.

Otherwise utilizing veg-oil fuel needs either an expert SVO service or biodiesel. Mixes and blends are usually a bad compromise. But mixes do have an advantage in winter.

Just like biodiesel, some kerosene or winterised petro-diesel fuel mixed with straight veggie oil reduces the temperature level at which it starts to gel. (See Using biodiesel in winter) More about fuel blending and blends.