The reason for falling oil prices explained (maye)

There is also discussion that Saudis are allowing oil prices to fall in order to hurt the Iranian economy (Saudi oil is cheaper to produce per barrel than Iranian oil). What I want to know is why diesel is running almost 80 cents a gallon more than gasoline? It annoys me to see local service stations advertising regular unleaded at $2.99 but still demanding $3.79 a gallon for diesel!