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

1. Use the oil just 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 gas;

3. Convert it to biodiesel.

The very first two techniques sound easiest, but, as so typically in life, it's not quite that simple.

1. Mixing it

Grease is far more thick (thicker) than either petro-diesel or biodiesel. The purpose of mixing it or blending 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 (like # 1 diesel) you're still using fossilfuel-- cleaner than many, but still unclean enough, many would state. Still, for every gallon of

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

People use numerous mixes, ranging from 10% veggie oil and 90% petro-diesel to 90% grease and 10% petro-diesel. Some people simply utilize it that way, begin up and go, without pre-heating it (that makes veg-oil much thinner), or even use pure vegetable oil 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 however you most likely won't 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 using pure petro-diesel or biodiesel for starts and stops. (See next.) In which case there's no requirement for the mixes.

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

Higher viscosity is not the only issue 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 engines are state-of-the-art devices with really accurate fuel requirements, particularly the more contemporary, cleaner-burning diesels (see The TDI-SVO controversy).

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

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

Just like biodiesel, some kerosene or winterised petro-diesel fuel blended with straight veggie oil lowers the temperature at which it begins to gel. (See Using biodiesel in winter season) More about fuel mixing and blends.