Today's efficient cars may help us to minimize fuel costs, but just how far can they take us on one tank? That's what RAC and Audi are finding out with their Record Road Trip. The Guinness World Record attempt to see how many countries can be visited on a single tank of fuel began this morning.

The vehicle being used for the journey is an Audi A6 TDI Ultra, chosen for its good fuel economy of 67.3 mpg (28.6 km/l) and large 73-l (16-gal) tank. The A6 will be unmodified, save for the use of fuel-efficient, low-rolling-resistance tires aimed at further improving fuel-efficiency.

With motoring journalist Andrew Frankel and racing driver Rebecca Jackson behind the wheel of the A6, the journey began at 9:47 am in Maastricht, the Netherlands. The route is said to have been carefully planned by the RAC to avoid high-fuel-usage areas such as congested towns and cities, motorways and mountains. It will take them through Belgium, Luxembourg, France, Switzerland, Lichtenstein, Austria, Germany and Italy toward the Balkans.

Frankel and Jackson must drive carefully to use as little fuel as possible and to achieve as high a mile per gallon figure as possible. They have a targeted average speed of 56 mph (90 km/h). It is thought that they will be able to travel for over 1,000 mi (1,609 km) using just one tank of diesel.

You can keep track of Frankel and Jackson's progress on Twitter @RecordRoadTrip or using the hashtag #RecordRoadTrip, and at