There are at least 3 ways to run a diesel engine on biofuel using veggie oils, animal fats or both. All 3 are utilized with both fresh and pre-owned oils.
1. Use the oil just as it is-- usually 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 fuel;
The first two approaches sound most convenient, however, as so frequently in life, it's not quite that easy.
1. Mixing it
Vegetable oil is much more viscous (thicker) than either petro-diesel or biodiesel. The function of blending it or blending it with other fuels is to decrease 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 (same as # 1 diesel) you're still utilizing fossilfuel-- cleaner than most, but still unclean enough, lots of would state. Still, for every single gallon of
grease you use, that's one gallon of fossil-fuel conserved, which much less climate-changing carbon in the atmosphere.
People use different blends, varying from 10% grease and 90% petro-diesel to 90% grease and 10% petro-diesel. Some individuals simply use it that way, launch and go, without pre-heating it (that makes veg-oil much thinner), and even use 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 a really hard and tolerant motor-- it will not like it but you most likely won't kill it. Otherwise, it's not wise.
To do it correctly you'll require what totals up 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 requirement for the blends.
Blends with numerous solvents and/or with unleaded gasoline are "speculative at finest", little or nothing is learnt about their impacts on the combustion characteristics of the fuel or their long-term effects on the engine.
Higher viscosity is not the only issue with using vegetable oil as fuel. Veg-oil has various chemical residential or commercial properties and combustion characteristics from the petroleum diesel fuel for which diesel engines and their fuel systems are created.
Diesel motor are high-tech makers with very accurate fuel requirements, particularly the more contemporary, cleaner-burning diesels (see The TDI-SVO debate).
They're hard but they'll only take so much abuse. There's no guarantee of it, however utilizing a blend of up to 20% veg-oil of great quality is said to be safe enough for older diesels, particularly in summer season.
Otherwise utilizing veg-oil fuel requires either an expert SVO option or biodiesel. Mixes and blends are typically a poor compromise. But blends do have a benefit in winter.
Just like biodiesel, some kerosene or winterised petro-diesel fuel blended with straight vegetable oil decreases the temperature at which it begins to gel. (See Using biodiesel in winter) More about fuel mixing and blends.
