I live in eastern South Dakota and we have had terrible trouble with fuel gelling since the switch to ULSD. We used to run straight #2 all winter with a dose of Power Service in temps down to -30 with no problems whatsoever. Now with the new fuel, no additives work. My truck has gelled, our farm tractors do several times a winter, as well as our semi. Running a strong blend of #1 helps, but several of our neighbors have had tractors and dump trucks plug up with straight #1 and at warmer temps than we used to run with no troubles. Seems hard to believe but I have called several additivie companies and they all tell me the same thing. Here in eastern SD, we get some of the worst diesel fuel there is in the US for winter operability. They have taken fuel samples from the pipeline that our area gets its fuel from and its cloud point is awfull. With a double dose of additive and a 50/50 blend of #1 and #2 still only gets us down to about -8 to -10. It's completely ridiculous, but we have to deal with it for a few months every winter. About the only cure is to park in a heated shop or garage over night. One thing that I have repeatedly been told about using additives and/or blending fuel, the fuel has to be warm when it's treated or blended. Around 40 or 50 degrees. They all told me if the fuel is too cold when its treated, it won't do any good. This also seems to help by our experience.