Limitations of Biodiesel

As well as noting the clear and numerous advantages of biodiesel, it wouldn't be very objective of us if we didn't note that there are some disadvantages concerned with using biodiesel.

  • It is not advisable to use pure biodiesel in cars manufactured prior to 1992, unless the rubber pipes and fuel components have been replaced with modern ones (newer cars do not use rubber parts). Rubber reacts with biodiesel over time, and using it for more than a month may cause complications to fuel pumps, hoses, o-rings, leading to fuel leaks and seal problems. These can either be replaced with steel or heavy duty rubber, or corrosion can be reduced by using a 20/80 regular diesel/biodiesel mix.
  • Biodiesel alone should be avoided in newer vehicles with DPF (particulate filters) fitted because it reacts with the chemical additive injected into the fuel system at intervals by the ECU (engine control unit). A 50/50 mix of regular diesel/biodiesel can still be used in these vehicles without having any adverse effects.
  • Biodiesel may start to solidify between 4-5°C (40°F) depending on the oil used, leading to cold weather starting problems. During the winter, a 50/50 mix of regular diesel/biodiesel should be used.
  • Biodiesel is an excellent solvent and will clean out the fuel system, fuel lines, injectors and the fuel tank. Although not a bad thing, it does mean that the cleared gunk often gets dumped into the fuel filter, which may clog and create rough running or a drop in performance. People often mistake a simple fuel filter blockage as engine damage due to using biodiesel. If a lack of acceleration or poor running is experienced after around 300 to 1000 miles of using biodiesel, then usually a fuel filter change is all that is needed. Once done, it only requires changing at the normal intervals (it is rare to experience subsequent filter blockages after the initial change over to biodiesel).
  • At present there just are not enough people using biodiesel to warrant manufacturer's taking the time and expense of running tests on their cars using this fuel. However, just because a vehicle isn't approved for biodiesel use doesn't mean it won't run trouble free using it. That said, running a new vehicle that is still under manufacturer's warranty on biodiesel is probably not a good idea, and if you choose to do so then at least make sure the fuel tank is full of regular diesel whenever it is taken in for servicing or warranty work.
  • If your car has never used biodiesel before it is sensible to start introducing it on a gradual basis. Start with a 25/75 biodiesel/regular diesel mix, then a 50/50 mix and then move on to a 75/25 mix. If everything seems fine, then during the summer months move onto biodiesel alone (but see the caution about cold weather starting).
  • If methanol is used in the biodiesel production, this can be made from biomass (such as wood) but most is made from natural gas, which of course is a fossil fuel. This goes against the grain slightly regarding biodiesel being a fully environmentally friendly fuel - unless etanol is used of course. Most ethanol is plant-based (although some is also made from petroleum) so technically it is greener to use this in the poduction (but this is more difficult and not for beginners).
  • Until consumer and manufacturer confidence reaches the right level through testing biodiesel in a variety of engine sizes and shapes, then it won't be widely available and so people are forced to manufacture their own supplies.