There's obviously a lot  more to it than that. Particularly the issue of how to start a cold vehicle using cold thick vegetable oil. There are a number of ways around this issue, which include blending the oil with diesel to thin it, or converting the vehicle to start and run on cold oil (known as single tank) or starting and warming up on diesel then switching over to vegetable oil  when the engine is warm enough (twin tank). There are pros and cons with each method.

Vehicles were not designed to run on vegetable oil so there are a number of issues you should know  and consider before going down this route. Some vehicles are more agreeable to being powered by vegoil than others - generally the older the vehicle, the more likely it is to run on vegoil without problems. Many pre 1998 cars will quite happily run on vegoil with only very minor modifications, this is where significant financial savings can be made. Other cars of the same vintage have components which are particularly sensitive and may break (especially if run on cold or insufficiently heated oil) requiring expensive repairs. Newer vehicles typically have higher fuel pressures and complicated engine management systems such as common rail, HDI or DCI diesel engines are more difficult to convert successfully. Certain cars will require more extensive conversion and more care and attention to prevent damage.

Next is the servicing of a vegoil vehicle. The service intervals should be reduced - the engine oil and filter should be changed more regularly to prevent engine damage while the fuel filter should be changed more regularly to avoid it clogging. It is good practice to always carry a spare fuel filter in the vehicle.

And finally this leads us to the fuel. The biggest savings by far, both financially and environmentally are to be had with used cooking oil. This is a case of collecting the oil from a local restaurant, pub, hotel, canteen etc. filtering it to remove the microscopic particles (to say 5 microns).  The oil is collected for free and since you can use 2,500litres per year before paying duty then it is potentially completely free, a saving of £50 to £80 per fill-up in a typical diesel car.

Another option is to buy oil in quantity like you would heating oil (either pumped into your tank or delivered in a 1m³ container) or to buy it at cash and carry or supermarkets (lots and lots of waste packaging, extra journeys and inconvenience to other shoppers who find the shelf empty). The use of new oil may save a 30p or 40p per litre but prices are rising as fast as diesel. Also there are wider sustainability issues associated with deforestation and using arable land to grow fuel.

To make a diesel vehicle run reliably on vegoil it is necessary to fit a conversion kit to the vehicle. The kit in simple terms heats the vegoil and thins it down to the same thickness/viscosity as diesel. This allows it to pass through the fuel delivery system in the same way as diesel and burn cleanly in the engine.

Conversion kits which enable vehicles to run solely on vegoil, known as ‘one tank’ kits, have been developed over the last 25 years by the German company Elsbett. Driving vehicles fitted with these kits is essentially no different compared to regular, day to day driving on diesel, with the exception of what you put in the fuel tank.  Not all diesel vehicles are suitable to convert to vegoil. Diesel vehicles fitted with most types of rotary pump produced by Lucas, CAV, Delphi, Stanadyne and Rotodiesel are not recommended for conversion by Elsbett. In addition, vehicles with common-rail direct injection and unitary direct injection engine designs cannot be generally converted with ‘one tank’ kits as they require start up on diesel.  Conversions involving ‘two tank’ kits are required for these vehicles.

To find a comprehensive list of the vehicles that can and cannot be converted it is best to visit the following database on the Elsbett website: www.elsbett.de/forms/ekit . (Click “Conversion Kits” on the center green bar, then click “PKW/Kleinbusse/Cars/Vans” on the center green bar).

There is more information available at Veg Oil Motoring and Dieselveg.com