The only problem I can see with Jet A 1 is it's low sulphur content. Sulphur aids in lubrication. My sister had a VW diesel and she used to put 1/2 a tank of Jet A 1 in the car. It wore out the fuel pump due to low sulphur content compared to D1 fuel. I believe the paraffin we use in our model diesels has more sulphur than D1.