http://forums.mercedesclub.org.uk/showthread.php?p=1311037#post1311037An expert advises:
"WVO biodiesel is made from WVO. the 'real' stuff (non WVO BD) that you can buy at some filling stations is less viscous and doesnt make your exhaust fumes smell like an old chip van!
there were quite a few articles on this a few years back when i first started to look into the idea of running on the WVO based biodiesel and, for whatever reason they all said it wasnt, technically, biodiesel in the true meaning of the term. they then went on to explain why. in a nutshell, the way the articles i was reading at the time said that yes WVO can be refined to the spec required to be used as road fuel (BS EN 590 IIRC) it is still WVO and NOT biodiesel."
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"proper biodiesel is probably fine. after all theres already about 7% of it in pump fuel anyhow. its the WVO 'biodiesel' that isnt great for CDI engines, from what i can gather, as its much thicker than 'proper' biodiesel, so puts more strain on the pump etc."
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"i dont know anyone who has managed to get the viscosity of their home brew diesel right as its always much thicker than pump diesel, and then you have to start thinning it down with normal diesel or other fuel which does seem to me to be defeating the object of the homebrew!"
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"apparently the 220cdi in OM611 guise WILL officially run (with the official options required) on PME based biodiesel, but NOT the WVO derived biodiesel, or any other type."
& on & on & on with similar bollocks.