Originally Posted by chris123
The important thing to remember is that there is a world of difference between your average marine / army / tractor diesel engine and the diesel engine in a modern diesel car.
A lot of work has gone in to achieving low emissions and high performance from ever smaller and lighter diesel engines. Amongst many other 'improvements' tolerances between components in fuel pumps and injectors have got much tighter.
In a previous life I worked for a filtration company developing fuel filters for a number of car manufacturers, and the fuel cleanliness requirements to achieve the design life for the fuel system components were extremely tight. Personally, I wouldn't add anything to diesel fuel that could effect viscosity / lubricity / filterability.
I agree you need to avoid thicker fuels. I changed the fuel filter on my Discovery - first time in 75,000 miles - it was spotless!!!
Some of the "modern" engines out there aren't so modern after all - the Passat I hired a few months ago still had the original 1.9tdi engine in it - yuch!!!
I know one bloke with one of the latest Mercs which he runs on neat cooking oil - he has a heated tank.
Lubricity is improved considerably by cooking oil. The US army have been using jet fuel/kerosene in all their diesel engines and they use lubricity enhancers to compensate - only needed in very hot countries though.