We very much recommend
the twin tank system. Here are the reasons why;
- The engine's fuel system gets a clean with mineral diesel every time
it goes through the purge and warm-up period. This keeps the fuel system healthy for longer.
- The engine is always started from cold on fuel with the correct viscosity, which
means it flows through the filter and fuel system correctly, minimising strain
on the injector pump and filter. This also ensures better fuel vaporisation
and cleaner burning, which in turn minimises the risk of coking the injectors
(clogging the nozzles with sooty deposits) and ring gumming (see below).
- The pump is lubricated properly during the warm-up period; the time when pump
axles tend to break with other systems due to poor lubrication.
- If there is a problem with the vegoil fuel system on a journey, (eg the filter becomes
blocked), it is possible to switch to the diesel system to complete the journey rather
than undertake repairs on the side of the road
Some vehicles are
happier being powered by vegoil than others. Generally,
indirect injection engines are best. Most cars from the early 1990s will
have indirect injection engines although many modern pickups and 4x4s
will also be powered by IDI engines. They have swirl chambers where
the fuel is injected giving very good atomisation of the fuel before
it is burned. Many cars of this vintage have Bosch VE rotary pumps
or equivalent which are great with vegetable oil. However some have more fragile
LUCAS/CAV injector pumps which are particularly
sensitive and may break, especially if run on cold or
insufficiently heated oil.
Direct injection engines are also good with vegetable oil, especially if using a
Bosch VP37 pump or equivalent. The fuel is injected directly into the
combustion chamber. The problem of ring gumming is an issue with DI engines.
This is caused by unburned vegoil running between cylinder walls and the pistons.
Over time this can become rubbery, preventing a good seal
between the piston rings and cylinder, resulting in loss of compression.
A secondary issue of ring gumming is engine oil polymerisation. This is where
vegoil gets into the engine oil and a reaction takes place which thickens
the engine oil. Ring gumming mostly occurs during cold starts when poorly
atomised fuel is injected into cold combustion chambers. The best way to avoid this
is to use a twin tank system where the engine is started and warmed up on diesel
before vegoil is introduced to the engine.
Later, common rail vehicles have higher fuel pressures and complicated
engine management systems which make them more difficult to convert
successfully. They are also expensive to repair. In our experience it
is best not to convert common rail engines.
The service intervals of a vegoil
vehicle should be reduced - the engine oil
and filter should be changed more regularly to prevent engine
damage. This is particularly important with direct injection vehicles to
avoid engine oil polymerisation as discussed above. The fuel filter
should be changed more regularly to avoid it clogging. It is sensible
to always carry a spare fuel filter in the vehicle.
And finally this leads us on 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) and pouring it straight into your fuel tank. You need
to make sure the oil is 'lightly' used to prevent it from being
fatty, watery or acidic. It must also be kept clean and dry. It can
take some effort to start with but this can be quite a slick operation
with the cooperation of an understanding chef. You visit regularly
to drop off some empty containers and collect some full ones. Since you
can use 2,500 litres per year before paying duty then
it is potentially completely free, a saving of £60 to £100
per fill up in a typical diesel car.
Another option is to
buy vegetable oil in bulk like you would heating oil
(either pumped into your storage tank or delivered in a 1m³
container). We do not recommended that you buy cooking oil from the
cash and carry or supermarkets (for many reasons including the
amount of waste packaging, extra journeys, inconvenience to other
shoppers and for ecological reasons).
For some really good, clear information about driving on vegetable oil, please visit Geoff's fantastic website
where you will find information and videos describing how a twin tank system works, driving on vegetable oil and filtering waste oil as well as pages and pages of background, hints and tips. All useful information if you are thinking of venturing into the world of vegoil motoring
Disclaimer
While every effort is taken to ensure that the information on this
site is accurate we accept no responsibility or liability for
any problems encountered while acting upon it.
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