In a bold move morrisons supermarket have been the first of the petrol retailers of 2012 to offer a  money off coupon, and it comes with the great name - Fuel Britannia.
For this deal you need to spend over £40 in store before the 15th January and you will receive a voucher for 6p off for each and every liter of petrol that you fill up with.  6p is a pretty generous offer and will save you around £3 on a full tank of petrol, so try and use it just before you run out of fuel.
The voucher needs to be used up before the 22nd of January, and there is a limit of 100 litres of fuel, so you cant go and fill up 50 odd jerry cans with petrol and expect to get money off each litre!
Hopefully this is a sign of things to come and more supermarkets will follow suit shortly.