The reason for the seasonal blends of gasoline can be placed at the feet of the good old federal government (EPA) and their pollution requirements. The oil companies would not do this unless they had to. Beyond this, the oil markets are rigged. When I used to read articles about the price of oil, one day supplies are plentiful and prices are trending down. Then a few days later supplies are restricted and prices are now trending up. No one seems to know, but they have no problems making things up. Or worse, they know what is occurring but will not tell the truth. Then of course there will always be a crown prince from an oil producing country who will wake up with a spastic colon and oil prices will shoot up 30%.