There are at least three methods to run a diesel engine on biofuel using vegetable oils, animal fats or both. All 3 are utilized 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 gas;

3. Convert it to biodiesel.

The first two methods sound most convenient, however, as so typically in life, it's not quite that easy.

1. Mixing it

Grease is far more viscous (thicker) than either petro-diesel or biodiesel. The purpose of blending it or mixing it with other fuels is to reduce the viscosity to make it thinner so that it streams more freely 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 utilizing fossilfuel-- cleaner than a lot of, however still unclean enough, many would say. Still, for every single gallon of

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

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

To do it properly you'll need 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 need for the blends.

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

Higher viscosity is not the only issue with utilizing veggie oil as fuel. Veg-oil has various chemical properties and combustion attributes from the petroleum diesel fuel for which diesel motor and their fuel systems are designed.

Diesel engines are state-of-the-art machines with really accurate fuel requirements, particularly the more modern, cleaner-burning diesels (see The TDI-SVO debate).

They are difficult however they'll only take a lot abuse. There's no guarantee of it, however utilizing a mix of as much as 20% veg-oil of good quality is said to be safe enough for older diesels, specifically in summer.

Otherwise using veg-oil fuel needs either a professional SVO service or biodiesel. Mixes and blends are normally a poor compromise. But blends do have a benefit in winter.

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