Using Vegetable oil as a diesel fuel

How it all started

  A very clever man called Rudolf Diesel invented a new type of engine that operated at a higher compression ratio and didn't have spark plugs. The first thing that he noticed was that it was about 30% more efficient than a petrol engine and, also, he could run it on vegetable oil! Very quickly, the engine became adapted for use with fossil fuels since they were, and still are, very much cheaper than vegetable oil and Rudolf's second idea became forgotten.

  Then along came Tony Blair and his chancellor of the exchequer, Gordon Brown, and they changed the fuel duties on fuels so that vegetable oil became a viable fuel source in the UK. Other countries, such as Germany, have been using vegetable oil as a fuel for many years and have developed sophisticated methods of adapting engines and processing fuels. Traditionally, biodiesel is the label attached to 'methyl esters of fatty acids', which is basically vegetable oil reacted with methanol, but the British government has broadened the scope of the definition of biodiesel to include straight vegetable oil or SVO so opening the field to use relatively unprocessed oils with much less processing waste and  energy consumption. Environmental campaigners are pushing for the greater use of sustainable fuels which have less harmful effect on the planet - biodiesel, in it's most unprocessed state, is one of the best options that we have.

What is vegetable oil?

  Vegetable oil comes in very many shapes and sizes, with varying properties. The most important consideration is melting point. The actual vegetable oil molecule is composed of three long carbon chains on a glycerol 'backbone' and it's properties are determined by the individual 'fatty acid' chains. Rapeseed oil, for example, may be composed of different combinations of about 6 different fatty acids and each one of these creates a unique molecule, with unique properties. Some waste oil contains 'free fatty acid', which is a result of water in fried food reacting with the triglyceride to split it up into it's four components. Waste oil also contains varying amounts of animal and fish oils which may be solid at room temperature in their natural state. As a breast of chicken, for example, is fried, oil diffuses out of the chicken and is replaced by oil from the fryer and as more and more chicken is fried, the concentration of chicken oil increases, thickening the oil until it may become solid.

  There are many different types of vegetable oil and each one has unique properties. The best one for use as a fuel is undoubtedly rapeseed oil as it is relatively thin, cheap to produce and easy to get hold of. A second best would be sunflower oil. If you go into a supermarket in the UK, rapeseed oil is the stuff in the cheap plastic bottles which sometimes has little yellow flowers on it.

Can it be used as a fuel for diesel engines?

  The answer is 'yes', but we have to be careful not to use it in the wrong way otherwise engine damage may occur. There are two schools of thought, both of which seem to work well. The first is to blend vegetable oil in with diesel or kerosene up to a ratio of about 20%, depending on what extra additives are used and what the ambient temperature is. The additive is used to compensate for the loss in ignition properties and to help keep the combustion cylinder parts clean. The second school of thought is to use a two tank system where the vehicle is started up on a thin, highly combustible fuel such as fossil diesel and then switched over to a second tank when the engine is nice and hot. Biodiesel is a third alternative and can be found blended with diesel at 5% in some petrol stations. Biodiesel is the scientifically approved derivitive of vegetable oil and is a relatively highly processed product which has a much lower viscosity than straight vegetable oil.

  Vegetable oil works much better in older vehicles which DO NOT have lucas injection pumps. We have created a database of over 150 vehicles that have been running on vegetable oil which has highlighted some of the successes and failiures that people have had. The database can be browsed by make or model to see if a particular vehicle is already running on vegetable oil and how well it runs.

Can vegetable oil harm the engine?

  Yes it can. It must be used within sensible limits and pushing these limits for convenience or cost will cause long term, or even immediate problems. Some of the conclusions that people have made regarding the use of vegetable oil as a diesel fuel have been contradictory and so there are no guarantees to be given. Some of the motor industry test labs found that vegetable oil accelerates coking of the engine, others found it had no detrimental effect in long term trials. One of the problems with this research is that none of the engines were used with 2 tank systems and so they were started from cold on vegetable 100% vegetable oil, which is a definite disadvantage. A recent report from Ricardo has shown that older, indirect engines give good performance statistics when running with a two tank system, with increased fuel efficiency and similar emmisions when compared with diesel.

  In addition to the resources mentioned above, goat industries has a discussion board that has highlighted some other problems that may be encountered. One of the problems that has been discovered through discussion is the effect that hot vegetable oil can have on the filter cartridge in the fuel system. Some cartridges seem to suffer from deterioration of the glue that binds the filter cloth to the metal retaining plate, which may be due to the high temperature of the fuel or the high acid content if waste oil is used. High acid content may also affect some of the engine parts and there has been some mention of injector needles becoming corroded from people running static electricity generators.

  Goat industries has endeavoured to produce high quality information based on extensive research into using vegetable oil as a fuel for diesel engines. The information published on this web site will enable people to use this fuel safely and protect the environment. One of our major concerns is that the engine must be protected and that the fuel should not be promoted at the expense of people's vehicles. Information on some other websites does try to push the limits of sensible use in an effort to save the planet, but we think that this will only back fire and give vegetable oil a bad name when the news of engines blowing up filters through.

 

Myths and legends of vegetable oil use

  There is a lot of rubbish talked about concerning these fuels. Some of it is a result of people trying to protect their 'secret' recipes and thereby creating mis-informative myths. One of these was the 'teaspoon full of white spirit in vegetable oil' on the top gear program - absolute rubbish! The 'white spirit' was supposed to be a special fuel additive. Beware of myths - lets create legends!

  Myth number 2. Not all diesel engines will run on a mix of 95% diesel and 5% white spirit. Again, absolute rubbish! We've heard of quite a few vehicles actually breaking down on this brew. Older vehicles, with indirect injection, without lucas pumps, are more compatible with higher concentrations of vegetable oil. White spirit can be added, but quite a bit more than 5% would be needed to have any effect.

  Some people mix vegetable oil with petrol and use it in a diesel engine! See Database

  We have heard of some vehicles travelling over 200,000 km on vegetable oil.

The pros and cons of using vegetable oil as a fuel

Pros:
  1. Environmentally friendly.
  2. Waste oil is cheaper.
  3. Smoother engine running - no 'knock'.
  4. Better lubrication.
  5. Less reliance on petro-chemicals.
  6. Enhanced street credibility.

 

Cons:
  1. May cause engine coking if misused.
  2. May invalidate vehicle warrantee.
  3. Exhaust smells of chips (unless cat. converter fitted).
  4. Have to pay tax to customs and excise
  5. Harder to start the engine in the morning
  6. Will destroy some injector pumps
  7. Only useful in older vehicles.