Thanks people. My oil burner does recirculate back to the tank but i take your warning seriously. I originally bought a vaporising oil stove (franco belge) to use in the spring and fall. That burns bio nicely, but as you say, it aint #2. I think i will leave the oil gun out of this and get a second tank just for the spring and fall. We dont burn much oil in the winter in any case. The wood boiler is too hot for the spring and fall, so thats when we burn oil-- about a 100 g a year.
The supplier did in fact assert that his cloud point was 17 deg, but in alternative energy, there is a lot of wishful thinking, so i thought to poll the experts.