Originally Posted by silentC
It seems that what has happened is that the petrol has expanded, as it does, because it was freezing the day I filled up and hot on this day. I had managed to fit more petrol in there than the tank could hold at the warmer temp, even though I had used a up a bit of it in the meantime.
So the moral to the story is that if you fill up on a cold day, you get more for the same price, because the mass to volume ratio goes up the colder it is. But make sure you don't overfill, or some of the profit runs down the drain. :o