I remember doing a fuels course many moons ago, finding out flashpoints, specific gravity, water content (yep all fuel has some) seeing how much FSII was in the fuel. It was interesting at the time as I could say yes/no as to wether we accepted the fuel or not, I expect they have a bit of kit now that does it all in seconds.
Diesel will wax, avoid Morrisons in the winter as their pumps are prone to jam/not cut out. Espically at the Fort nr Glasgow as I found out to my cost, stinking all day after a little blow back.