There are at least 3 methods to run a diesel motor on biofuel utilizing 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 grease);

2. Mix it with kerosene (paraffin) or petroleum diesel fuel, or with biodiesel, or blend it with a solvent, or with fuel;

3. Convert it to biodiesel.

The first 2 techniques sound easiest, however, as so often in life, it's not quite that easy.

1. Mixing it

Grease is a lot more thick (thicker) than either petro-diesel or biodiesel. The function of blending it or mixing it with other fuels is to reduce the viscosity to make it thinner so that it streams more easily through the fuel system into the combustion chamber.

If you're blending veg-oil with petroleum diesel or kerosene (same as # 1 diesel) you're still using fossilfuel-- cleaner than a lot of, however still unclean enough, lots of would say. Still, for each gallon of

grease you use, that's one gallon of fossil-fuel saved, which much less climate-changing carbon in the environment.

People utilize numerous mixes, varying from 10% vegetable oil and 90% petro-diesel to 90% grease and 10% petro-diesel. Some people simply use it that way, start up and go, without pre-heating it (that makes veg-oil much thinner), or even use pure grease 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 will not like it but you probably won't kill it. Otherwise, it's not smart.

To do it effectively you'll need what amounts to an SVO system with fuel pre-heating anyhow, preferably using pure petro-diesel or biodiesel for starts and stops. (See next.) In which case there's no requirement for the blends.

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

Higher viscosity is not the only issue with using grease as fuel. Veg-oil has different chemical homes and combustion qualities from the petroleum diesel fuel for which diesel engines and their fuel systems are created.

Diesel engines are high-tech devices with really accurate fuel requirements, specifically the more contemporary, cleaner-burning diesels (see The TDI-SVO controversy).

They're difficult but they'll only take a lot abuse. There's no warranty of it, however utilizing a mix of approximately 20% veg-oil of excellent quality is said to be safe enough for older diesels, especially in summer.

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

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