It is noticeable that the differential between Diesel and Unleaded has widened in France, where diesel has always been cheaper than petrol – whereas in the UK diesel is usually more expensive.
As always best prices tend to be available from major hypermarkets and many small local supermarket chains – autoroutes and many “branded” fuel stations are usually more expensive.
Another issue for driving in France is autoroute tolls which can add a significant cost to your trip – e.g. a one-way trip by car from Calais to Avignon via autoroute can cost over £60 in tolls – however this is far faster than N roads and can save additional overnight hotel charges etc.
There are however some toll-free autoroutes which can save you some if not all of these costs – and for example if you were heading for Eastern France, Alsace, Jura and the Alpes the you should consider using the toll-free autoroutes in Belgium, Luxembourg and Germany which can offer both fast and free travel.
Plus a detour via Luxembourg can offer more savings – e.g. in September 2010 the cost per litre for diesel was €0.99 (£0.88) and for unleaded was €1.14 (£1.02).