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

1. Use the oil just as it is-- typically 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 gas;

3. Convert it to biodiesel.

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

1. Mixing it

Grease is much more viscous (thicker) than either petro-diesel or biodiesel. The function of blending it or mixing it with other fuels is to decrease the viscosity to make it thinner so that it flows more freely through the fuel system into the combustion chamber.

If you're mixing veg-oil with petroleum diesel or kerosene (same as # 1 diesel) you're still using fossilfuel-- cleaner than many, but still unclean enough, many would say. Still, for every gallon of

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

People use various blends, varying from 10% grease and 90% petro-diesel to 90% vegetable oil and 10% petro-diesel. Some individuals just use it that way, begin up and go, without pre-heating it (which makes veg-oil much thinner), or perhaps use pure veggie 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 a very hard and tolerant motor-- it will not like it however you most likely won't eliminate it. Otherwise, it's not smart.

To do it appropriately you'll need 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 various solvents and/or with unleaded gasoline are "experimental at finest", little or absolutely nothing is known about their effects on the combustion attributes of the fuel or their long-lasting impacts on the engine.

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

Diesel engines are state-of-the-art devices with extremely precise fuel requirements, especially the more modern, cleaner-burning diesels (see The TDI-SVO debate).

They are difficult but they'll just take a lot abuse. There's no warranty of it, however utilizing a mix of up to 20% veg-oil of excellent quality is said to be safe enough for older diesels, particularly in summertime.

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 cold weather condition.

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