Not sure if this has ben done before; I purchased one of these recently http://www.ecomagnets.com/thermoflow.htm It's basically a magnet that you strap to the fuel line of you're boiler. Claims that it increases fuel efficiency etc etc. It also claims it was discovered during WWII, to make bombers travel further. I had the efficency of a kerosene boiler tested with it on recently, it was 91%, I had another boiler tested and it was 89% (without magnet). But the latter was older. Unfortunately was not there at the time of testing so could not test the same boiler with and without block on it. Any thoughts?? PS; it's not cheap either!!