There are at least 3 methods to run a diesel motor on biofuel using veggie oils, animal fats or both. All three are used with both fresh and pre-owned oils.
1. Use the oil just as it is-- typically 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;
3. Convert it to biodiesel.
The first 2 approaches sound most convenient, but, as so typically 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 blending it with other fuels is to reduce 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 (very same as # 1 diesel) you're still utilizing fossilfuel-- cleaner than most, but still not clean enough, many would say. Still, for each gallon of
veggie oil you utilize, that's one gallon of fossil-fuel conserved, and that much less climate-changing carbon in the atmosphere.
People utilize numerous blends, varying from 10% vegetable oil and 90% petro-diesel to 90% grease and 10% petro-diesel. Some individuals simply use it that method, begin up and go, without pre-heating it (which makes veg-oil much thinner), or even use pure grease 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 a really difficult and tolerant motor-- it won't like it but you probably will not eliminate it. Otherwise, it's not wise.
To do it appropriately you'll require what totals up to an SVO system with fuel pre-heating anyway, preferably utilizing pure petro-diesel or biodiesel for starts and stops. (See next.) In which case there's no requirement for the mixes.
Blends with different solvents and/or with unleaded fuel are "speculative at finest", little or absolutely nothing is understood about their effects on the combustion qualities of the fuel or their long-lasting impacts on the engine.
Higher viscosity is not the only problem with using grease 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 developed.
Diesel engines are modern makers with really exact fuel requirements, particularly the more modern-day, cleaner-burning diesels (see The TDI-SVO debate).
They're tough however they'll just take a lot abuse. There's no assurance of it, but utilizing a blend of as much as 20% veg-oil of great quality is said to be safe enough for older diesels, especially in summer.
Otherwise utilizing veg-oil fuel needs either an expert SVO option or biodiesel. Mixes and blends are usually a poor compromise. But mixes do have an advantage in cold weather condition.
As with biodiesel, some kerosene or winterised petro-diesel fuel mixed with straight veggie oil reduces the temperature level at which it starts to gel. (See Using biodiesel in winter) More about fuel blending and blends.