Originally Posted by Phobia
The gas stations themselves aren't to blame for the patterns questioned in the OP.
Of course they are. The link Donger provided spells it out clearly.
They raise the price in anticipation of increased wholesale costs, even if that means selling gas they already bought for a higher margin, but they lower prices more slowly so as not to sell for a lower margin.
Plainly put, the issue isn't the slow decline of gas prices, its the rapid increase. And it happens rapidly because it briefly allows for higher profit margins.