When I got my first diesel, a 1985 Chevy Suburban, I was told of the gelling problem, decided to do a little experiment. Took a sample of diesel when I filled up, Texaco diesel winter #2, stuck it in the freezer, -2 degrees, checked after 2 days, it was cloudy, but not solid. Poured some out, and it was thicker than normal. Used this as a point of reference for adding kerosene when it got cold, like down in the 20's for several days. This is the only way I know of checking the cloud point of diesel at home. For my present F350 diesel, during the winter I keep the front tank 1/2 diesel, 1/2 kerosene, when it gets cold, i will run on the front tank the last couple of miles on the way home to get mixed fuel in the lines and pump for the night, and run it for the first couple miles in the morning until everything warms up. It seems to work as I have always able to get it started. Power is down slightly with the mix and it rattles a little more. I keep my tractor in the garage so it hasn't been a problem.