hahaha very nice and true !
sorry if i 've confused
We have no biodiesel here it's forbiden by the law because can't be taxed as a petrol derivated product.
the same for vegetable oil.
little or local business doing that do not exist.
In any case the piston you saw ran only with diesel fuel from the service station.
the bad injection spray pattern did what you can see.
like the cold start device giving too much advance all the time.
the bad viscosity do that because the diesel is not sprayed but make drips wich can't burn easily and create very high pressure spots.
it's like pinging on a gas engine.
you need to readjust all parameters.
The "normal" diesel fuel is heated and cooled here on the cars : the good density and viscosity is necessary to control the quality of the combustion :
all the idi diesel from peugeot citroen range rover have electric fuel heaters and heat exchangers to heat up the fuel.
and nowadays on direct injection diesel there are fuel heaters and coolers for the same reason and because the fuel need to be cooled its at very high temp in the very high injection system (1500 to 2000 bars).
i want to stress on the fact a good fuel injection system is the key whatever the fuel you use.
you must control the viscosity injection time and vaporization because the properties change from one fuel to an other.