In general biodiesel will run any Diesel vehicle. It can be used as 100% biodiesel or blended with mineral diesel in any proportion. Mileage and performance are generally very similar: most people don't report any change after making the switch. Biodiesel is a good lubricator and some studies suggest it can prolong engine life.

There are however a few things you should know about the difference between biodiesel and mineral diesel in practice:

1. Biodiesel is a great solvent. this means that it attacks rubber hoses and seals. This is not a problem with post-about-1994 vehicles as they have biodiesel-compatible materials. With older vehicles we have seen flexible fuel lines and return lines slowly swell and lose their grip. Luckily replacement of these hoses is an easy job. Seals inside the fuel pump would be harder to replace but we have not heard evidence of problems with these. The solvent quality of biodiesel also means that it will dissolve any gunk in your fuel tanks and more than likely deposit it in your fuel filter. The solution: change fuel filter within 1000 miles of switching to biodiesel (or when problems such as sluggish performance manifest themselves). Almost all the reported problems we have come across with biodiesel have either been due to very poor quality fuel (not from us!) or due to a blocked fuel filter.

2. Winter starting. Biodiesel gels at a higher temperature than mineral diesel so you might get grumpy starting below zero, more noticeably below -5 C. You can add winterising agent to the biodiesel but the easiest thing is generally to add a proportion (say 10 or 20 percent) of mineral diesel to the biodiesel in winter. The mineral diesel you buy in winter contains a proportion of winterising agent itself. For UK winters this is generally fine and we have started vehicles on 100% biodiesel in -10c. Starting problems in winter are generally more to do with poor glow plugs or other engine issues than fuel per se.

3. High pressure systems. Diesel engines have changed a lot recently with the introduction of common rail and unit injector systems characterised by electronic control with small solenoid valves and sensors, and also by much higher pressures. The older engine system with distribution pumps have been extensively tested with good results on biodiesel. The higher pressure systems are less generic than older systems and its therefore harder to extrapolate results for one manufacturer to cover a range of engines. Manufacturers have not necessarily tested their systems on biodiesel and hard data is difficult to come by. Therefore we advocate caution with these systems and the use of a blend of biodiesel with mineral diesel. B20 (20% biodiesel) is a good starting point. Many of our clients have chosen to run 100% biodiesel in these engines however with good results.

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