I have jelled at minus 40. It sucks and depending on where your at when it happens it can be life threatening. There are towns here this week that are completely cut off with roads closed for the second day. When bad things happen, sometimes, there is no help. Usually when they gel the filters wax up and you have to replace them. When getting fuel in bulk like that, the most common way here is to order an appropriate amount of Number 1 diesel. If your getting 1000 gallons, order 300 gallons of number 1. Most fuel wholesalers can give you the formula to get to the temp you want to be covered to. Some guys will treat to minus 20 so it will pump and then treat with Power Service by the tank when it is colder than that. This prevents having to burn high treat fuel in warmer weather which gives less power and number 1 is more expensive, at least here.