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

3. Convert it to biodiesel.

The first two techniques sound most convenient, but, as so frequently in life, it's not quite that basic.

1. Mixing it

Grease is a lot more viscous (thicker) than either petro-diesel or biodiesel. The function of mixing it or blending it with other fuels is to reduce 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 utilizing fossilfuel-- cleaner than most, but still unclean enough, many would state. Still, for every gallon of

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

People utilize various blends, ranging from 10% veggie oil and 90% petro-diesel to 90% grease and 10% petro-diesel. Some people simply utilize it that way, launch and go, without pre-heating it (which makes veg-oil much thinner), or even use pure veggie 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 difficult and tolerant motor-- it will not like it however you most likely won't kill it. Otherwise, it's not wise.

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

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

Higher viscosity is not the only issue with using grease as fuel. Veg-oil has different chemical homes and combustion characteristics from the petroleum diesel fuel for which diesel engines and their fuel systems are designed.

Diesel motor are modern makers with very exact fuel requirements, especially the more modern-day, cleaner-burning diesels (see The TDI-SVO debate).

They are difficult but they'll only take so much abuse. There's no warranty of it, however using a mix of up to 20% veg-oil of good quality is stated to be safe enough for older diesels, specifically in summertime.

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

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