In the last couple of months I've noticed that the price of gasoline sometimes varies by as much as 35 cents a gallon from one station to the next.

Normally the price a station charges is based on the wholesale price of it's last delivery. If the wholesale price drops, then the station will normally lower their price at the pump to reflect the decrease.  Conversely, if the wholesale price increases, they will bump the retail price up.

Some stations sell more gas than others. They are known in the trade as "pumpers."  They may receive deliveries more than once in a day. Other stations may only receive deliveries once a week or so.

So when you see a wide range of prices check out the "pumpers."  If they are high then go to the lower-volume stations to buy your gas. They may not bump up the price for a few days after the pumpers react to the increase.

On falling prices check out the pumpers. They'll have the best prices!