Unlike France, German petrol prices are not in any way monitored by the state. Every petrol station is free to set its own price. In fact, I have seen the manager of my local petrol station out in the forecourt with binoculars looking at the prices at a station a few hundred yards up the road so that he can react immediately to any changes. This makes the petrol prices in Germany very volatile and they can change on an hourly basis. Consequently, even German websites have difficulty in keeping up with price information, often being a day or two behind actual current prices.
To be reliable, the source of information must therefore be on a real time basis. The only one like that that I have found is that of the '
OIL' petrol company. If you click on to 'Tankstelle finden' on the right of that page, enter a relevant postal code (or the name of the town using the 'Detailsuche' function), and then on to 'Kraftstoffpreise' in the next window you will get the up-to-the-minute prices at that the particular petrol station.
As I said, prices here can easily go up and down within the space of a few hours, but on the whole Sundays and Monday mornings are cheapest. The differences can be quite dramatic - up to 8 cents per litre.
There was, in fact, an extreme case reported last weekend where one petrol station that was slowly running out of one grade simply raised the price to 9.99 Euro a litre only to drop back to something more realistic later. The petrol company later apologized for the action of the manager and agreed to pay compensation to those customers involved.