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

1. Use the oil simply 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 most convenient, however, as so frequently in life, it's not rather that simple.

1. Mixing it

Vegetable oil is much more thick (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 streams more easily through the fuel system into the combustion chamber.

If you're mixing veg-oil with petroleum diesel or kerosene (exact same as # 1 diesel) you're still utilizing fossilfuel-- cleaner than most, however still unclean enough, many would state. Still, for every single gallon of

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

People utilize numerous blends, ranging from 10% vegetable oil and 90% petro-diesel to 90% veggie oil and 10% petro-diesel. Some people simply utilize it that way, launch and go, without pre-heating it (which makes veg-oil much thinner), and 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 an extremely hard and tolerant motor-- it will not like it but you most likely will not kill it. Otherwise, it's not wise.

To do it correctly you'll require 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 need for the blends.

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

Higher viscosity is not the only problem with using veggie oil as fuel. Veg-oil has different chemical homes and combustion qualities from the petroleum diesel fuel for which diesel motor and their fuel systems are developed.

Diesel motor are modern machines with extremely precise fuel requirements, especially the more contemporary, cleaner-burning diesels (see The TDI-SVO controversy).

They are difficult but they'll only take so much abuse. There's no guarantee of it, however using a blend of as much as 20% veg-oil of excellent quality is stated to be safe enough for older diesels, especially in summer.

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

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