In spanish http://journeytoforever.org/es/biodiesel_cav.html
Vegetable oil can be used as diesel fuel just as it is, without being converted to biodiesel.
The downside is that straight vegetable oil (SVO) is much more viscous (thicker) than conventional diesel fuel or biodiesel, and it doesn't burn the same in the engine -- many studies have found that it can damage engines.
BUT it can be done properly and safely -- IF you get a professional engine conversion. (See below.)
There are other approaches, here are the main ones:
1. Just put it in and go.
2. Mix it with diesel fuel or kerosene then just put it in and go.
3. Blend it with an organic solvent additive or with what some companies call "our secret ingredient that we'll tell you about if you pay us" (several versions) or with up to 20% gasoline (petrol), just put it in and go.
4. The only way to use veg-oil is in a properly installed two-tank system where the oil is pre-heated and you start up and shut down on diesel fuel (or biodiesel).
We've never had much time for Nos. 1 to 3 (more below), and we've had a two-tank SVO kit for a couple of years that pre-heats the oil and switches the fuel, but we never used it. They do work, but we just didn't think it solved the problem very well, and the more we learnt about it the more we didn't think so. (More about two-tank SVO systems.)
Along with many others, especially in Europe, we think pre-heating the oil is still not enough to ensure that it will combust properly inside the engine. It needs a complete system including specially made injector nozzles and glow plugs optimised for veg-oil, such as the professional single-tank SVO kits from Germany. Then you really can just put it in and go.
In March 2005 we installed a single-tank SVO system from Elsbett Technologie in our TownAce (1990 Toyota TownAce 1.9-litre 4-cyl turbo-diesel 4x4 van). The kit includes modified injector nozzles, stronger glow plugs, dual fuel heating, temperature controls and parallel fuel filters, and it does just what it claims to do.
There's no waiting or switching fuels from one to the other, just start up and go, stop and switch off, like any other car. It starts easily and runs cleanly from the start, even at sub-freezing temperatures. It can use SVO or biodiesel or petro-diesel or any combination of the three.
The professional single-tank SVO kits are the only SVO kits we recommend. Read on and we'll tell you why. We'll tell you about the other available options too.
See: Single-tank SVO systems.
SVO - straight vegetable oil used as diesel fuel (usually new oil, fresh, uncooked)
PPO - pure plant oils, same as SVO: PPO is the term most often used in Europe
WVO - waste vegetable oil (used cooking oil, "grease", fryer oil, probably including animal fats or fish oils from the cooking)
UCO - used cooking oil (what we called it in the first place until everyone started calling it WVO, even if it wasn't necessarily all vegetable)
IDI - Indirect Injection diesel engines: the fuel is injected into a pre-chamber or swirl-chamber before going on to the combustion chamber. Pre-chamber engines are more tolerant of SVO than swirl-chamber engines.
DI - Direct Injection diesel engines: the fuel is injected straight into the combustion chamber. DI diesels are less tolerant of SVO than IDI engines (see The TDI-SVO controversy). Types of DI diesels:
TDI - Turbo Direct Injection
CDI or CRD - Common-rail Direct Injection
PDI or PD - Pumpe Düse Unit Injection (Direct Injection, each injector has its own pump)
The basic choice for running diesels on biofuels:
* make biodiesel and just use it, no need to convert the engine, or
* convert the engine so you can run it on SVO -- no need to process the fuel.http://en.wikipedia.org/wiki/Vegetable_oil_fuel