There are at least 3 methods to run a diesel motor on biofuel utilizing veggie oils, animal fats or both. All three are used with both fresh and pre-owned oils.

1. Use the oil just 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 gasoline;

3. Convert it to biodiesel.

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

1. Mixing it

Grease is far more viscous (thicker) than either petro-diesel or biodiesel. The function of mixing it or blending it with other fuels is to lower the viscosity to make it thinner so that it flows more easily 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 a lot of, but still unclean enough, numerous would say. Still, for every gallon of

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

People use various blends, varying from 10% grease and 90% petro-diesel to 90% grease and 10% petro-diesel. Some individuals just use it that way, launch 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 really tough and tolerant motor-- it will not like it but you probably will not eliminate it. Otherwise, it's not smart.

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

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

Higher viscosity is not the only problem with utilizing veggie oil as fuel. Veg-oil has different chemical properties and combustion attributes from the petroleum diesel fuel for which diesel engines and their fuel are created.

Diesel motor are modern devices with very accurate fuel requirements, especially the more modern, cleaner-burning diesels (see The TDI-SVO controversy).

They're tough but they'll just take a lot abuse. There's no warranty of it, but using a blend of approximately 20% veg-oil of great quality is said to be safe enough for older diesels, especially in summer.

Otherwise using veg-oil fuel needs either an expert SVO solution or biodiesel. Mixes and blends are normally a poor compromise. But mixes do have a benefit in cold weather condition.

As with biodiesel, some kerosene or winterised petro-diesel fuel blended 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.