Kerosene, also known as 28 second oil. Most domestic systems run on kerosene because it provides a cleaner and more efficient burn for your home. Gas oil (red diesel), also known as 35 second oil, is more commonly used in agriculture and industry. Gas oil is less combustible than kerosene and has more carbon atoms.
There is, you will notice, fellow contributors, a seven second 'difference' in viscosity, between the two fuels, as measured in a rheometer.
My original question is still, therefore, valid.