To get into work each day I pass under I-95 at a fairly major intersection. Like pretty much all such locations there are a bunch of gas stations there. The standard mode of opperation is for them to change their prices once or twice a week, but they don't do it all at the same time. I've seen up to a 24 delay between the first change and the last.
Typically, I just drive till the light comes on the dash telling me that I need to get more gas, but when I see a price change where the stations are going up in price but haven't all gotten there yet I fill up regardless of how much go juice I have left in the tank.
Just did this tonight. All the stations on the block were at $2.41/gal. save for one which was still at $2.33/gal.
It's nice to feel like I saved at least a little.