CAUTION: Volkswagen does not approve the use of more than 5% biodiesel
on TDI vehicles sold in North America, and does not approve the use of
straight vegetable oil (SVO) or waste vegetable oil (WVO) at all. Use
of unapproved fuels is considered "misfueling". If there is a fuel
system related failure, and misfueling is found to be involved, any
damage may not be covered under warranty.
If you wish to use such fuels on an "I am my own warranty" basis, you
should be made aware of the risks involved. The process of making
biodiesel inherently involves alcohol, water, glycerine, lye, and
byproducts. Even tiny amounts of contamination can result in severe
damage to the high-pressure fuel injection components. Biodiesel must
conform to ASTM standards. "Home-brewers" generally have no practical
way to check whether their biodiesel conforms to standards.
Vegetable oil that has not been chemically transformed into biodiesel
generally has a viscosity which is much higher than the fuel injection
system is designed for, which puts more stress on the system. This is
of particular importance on "common-rail" or "pumpe-duse" fuel
injection systems (i.e. all 2004 and later North American models), and
the conventional wisdom is that vegetable oil is not to be used in
these engines. People wishing to install "kits" to fuel their vehicle
with vegetable oil are strongly urged to take into account whether a
particular "kit" is tailored specifically for their particular vehicle
and engine, whether the kit manufacturer offers a warranty on only the
kit or on the complete converted engine, and whether the kit has any
type of independent third-party approvals. Absence of a "kit" for a
particular engine should be interpreted as that engine being
unsuitable for operation on vegetable oil.
This disclaimer is not meant to incite panic, nor to steer people away
from Biodiesel/WVO/SVO. It's intended to educate, and to warn. Enjoy
using alternative fuels and feel free to use Biodiesel in amounts over
5% or WVO/SVO, but do so with the understanding that
fuel related issues may not be covered under warranty should you have a
Biodiesel FAQ for more info.
Also remember that what you are reading here on the Internet may not always be correct
Some people have ideas and suggestions which may or may not be
accurate. Please use your
own judgment when taking the advice of others.