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

1. Use the oil just as it is-- generally 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 gasoline;

3. Convert it to biodiesel.

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

1. Mixing it

Grease is a lot more thick (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 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 using fossilfuel-- cleaner than most, but still unclean enough, numerous would say. Still, for every gallon of

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

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

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

Blends with various solvents and/or with unleaded gasoline are "speculative at finest", little or 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 problem with utilizing veggie oil as fuel. Veg-oil has various chemical residential or commercial properties and combustion attributes from the petroleum diesel fuel for which diesel motor and their fuel systems are designed.

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

They're tough but they'll just take a lot abuse. There's no assurance of it, but using a blend of up to 20% veg-oil of great quality is said to be safe enough for older diesels, especially in summer season.

Otherwise using veg-oil fuel needs either a professional SVO solution or biodiesel. Mixes and blends are generally a bad compromise. But mixes do have an advantage in winter.

Just like 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) More about fuel mixing and blends.