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 pre-owned oils.

1. Use the oil simply as it is-- generally called SVO fuel (straight grease);

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

3. Convert it to biodiesel.

The first 2 approaches sound most convenient, however, as so often in life, it's not quite that basic.

1. Mixing it

Vegetable oil is far more viscous (thicker) than either petro-diesel or biodiesel. The function of blending 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 blending veg-oil with petroleum diesel or kerosene (like # 1 diesel) you're still utilizing fossilfuel-- cleaner than many, but still unclean enough, many would state. Still, for every single gallon of

vegetable oil you utilize, that's one gallon of fossil-fuel conserved, which much less climate-changing carbon in the atmosphere.

People utilize various mixes, varying from 10% grease and 90% petro-diesel to 90% veggie oil and 10% petro-diesel. Some individuals simply utilize it that way, begin up and go, without pre-heating it (that makes veg-oil much thinner), or perhaps utilize 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 an extremely hard and tolerant motor-- it will not like it but you probably will not kill it. Otherwise, it's not smart.

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

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

Higher viscosity is not the only problem with using grease as fuel. Veg-oil has different chemical residential or commercial properties and combustion characteristics from the petroleum diesel fuel for which diesel motor and their fuel systems are designed.

Diesel motor are high-tech makers with very exact fuel requirements, specifically the more contemporary, cleaner-burning diesels (see The TDI-SVO debate).

They're hard however they'll only take so much abuse. There's no assurance of it, however using a blend of approximately 20% veg-oil of good quality is stated to be safe enough for older diesels, particularly in summer.

Otherwise using veg-oil fuel needs either a professional SVO option or biodiesel. Mixes and blends are normally a bad compromise. But blends do have a benefit in cold weather.

Similar to biodiesel, some kerosene or winterised petro-diesel fuel combined with straight grease lowers the temperature level at which it begins to gel. (See Using biodiesel in winter) More about fuel blending and blends.