To be fair, I think I messed up. Bought diesel end of August as I was out, obviously got summer grade, and it's waxing up when it gets to 0 deg C. Mainly notice as I always fill up with filter funnels, so you can see it not pouring.   Any good additives that will help, or get another small delivery now, and the storage tank will be mixed up roughly 1/3rd summer diesel & 2/3rd winter grade diesel?