Biodiesel engine conversion

Posted by Krzysztof Lis on March 28, 2008

If you ever thought about using biodiesel as an engine fuel, you might thought also what conversion do you need to use this fuel safely. This article answers your question – if it’s required to convert your car to biodiesel and how to do it!

First of all, I must say, that most vehicle manufacturers won’t guarantee trouble-free operation if you use fuel blends of more than 5% biodiesel. I believe that they’re just afraid. Biodiesel is somehow standardized in EN 14214 and ASTM D6751. But biodiesel made at home may not fulfill the requirements stated in those documents. So engine manufacturers aren’t sure if biodiesel won’t harm your engine. If they don’t want to be sued, they need to inform you that adding more than 5% biodiesel to your fuel is forbidden. It’s as simple as that.

You shouldn’t be surprised that many drivers all across the world use biodiesel succesfully. Some of them even use the B100 blend with no trouble at all. Did they convert their engines somehow?

No, they didn’t!

The biodiesel is very similar to petrodiesel. It has similar viscosity, heating value, density and so on. The only important difference is its cold resistance. At low temperatures the biodiesel solidifies. The exact temperature at which biodiesel will make your fuel filter clogged depends on what the biodiesel is made of. It’ll start earlier (in higher temperature range) if the biodiesel is made of animal fats (which are solid in room temperature!). Put some biodiesel sample to your freezer and observe how it reacts to the cold temperature. If it becomes cloudy, you probably can use it in that temperature. If it becomes solid, you can’t.

Biodiesel is also much better solvent than petrodiesel. Because of that it dissolves many impurities that gathered along fuel lines during the time you used petrodiesel. So soon after you switch to biodiesel your fuel filter will need to be replaced with a clean one. Biodiesel will also degrade gaskets and fuel hoses made of natural rubber! This is especially dangerous in cars made before 1992 or so. But you may not have to worry – those parts also degrade by themselves, so they need to be replaced from time to time. If they were replaced in your car, they might be replaced with parts made of biodiesel-resistant material, like FKM.

There are also people who call vegetable oil the biodiesel. Using vegetable oil in your diesel engine indeed does require some engine modification. I wrote about it in the article Vegetable oil engine modifications.