The real difference in tempature change has to do with the tankers making the fuel dump. If ambient temp is hot/cold when the fuel is dumped then it will change the temp of what is in the storage tank no matter the time of the day. Over a period of time the fuel will return to the ground temp. Anyone have a geothermal heat pump? The earth has an underground temp of approximately 55* year round at the level that the geothermal system feild is installed.
Buying while they are dumping fuel or have just dumped fuel does stir up any trash in the tanks. I will never buy gas where I see the tanker dumping.
