Can a Diesel Aircraft engine be run on Car Diesel?
In at least some cases, yes. Continental's CD-155 diesel engine will run on auto diesel, Jet A or any mixture of both:


  The CD-155 is certified for the use of both jet fuel and diesel (DIN
  EN590) and is running with the two fuels in any mixture ratio.


EN590 is the European standard for auto diesel. The Gemini 125 engine can run on Jet A and diesel according to their website, as can the Austro AE300. So it seems that in general, aircraft diesel engines can indeed run on auto diesel.