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

1. Use the oil simply as it is-- usually 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 fuel;

3. Convert it to biodiesel.

The first two methods sound simplest, but, as so typically in life, it's not quite that easy.

1. Mixing it

Vegetable oil is a lot more viscous (thicker) than either petro-diesel or biodiesel. The purpose of mixing it or mixing 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 mixing veg-oil with petroleum diesel or kerosene (like # 1 diesel) you're still using fossilfuel-- cleaner than the majority of, however still unclean enough, many would say. Still, for each gallon of

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

People use numerous blends, ranging from 10% grease and 90% petro-diesel to 90% vegetable oil and 10% petro-diesel. Some people simply use it that way, start up and go, without pre-heating it (which makes veg-oil much thinner), or even use pure vegetable oil 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 eliminate it. Otherwise, it's not wise.

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

Blends with numerous solvents and/or with unleaded gasoline are "experimental at best", little or absolutely nothing is learnt about their effects on the combustion attributes of the fuel or their long-lasting effects on the engine.

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

Diesel engines are high-tech machines with very accurate fuel requirements, especially the more contemporary, cleaner-burning diesels (see The TDI-SVO debate).

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

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

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