Here in Canada you can rely on it that gas prices will jump immediately before a long weekend.
Example: In Edmonton, gas prices have been 80 cents a litre for a number of weeks. Oh so predictably on Thursday this week the price jumped to 85 cents a litre, just in time for the Remembrance Day long weekend. Jeez, we should have the lowest prices in the country, we're literally floating on crude oil here.
Don't know if they do this in your neck of the woods, but another stunt 'big oil' pulls is this business of deducting 3.5 cents per litre at the pump. They all do it so - why? Just put the bloody price on the sign and leave it at that.
There, I feel better now. :-)