According to Official Guinness Records,
The greatest distance driven on a single standard tank of fuel is 2,545.80 km (1,581.88 miles) by a Volkswagen Passat 1.6 TDI BlueMotion, in an event organized by 'Auto Motor i Sport' (Croatia). It was driven by Marko Tomac and Ivan Cvetkovic (both Croatia) within Croatia, between 27 and 30 June 2011.
Only Croatian roads were taken during the attempt. The average consumption amounted to 3.08 l/100 km (91.71 UK mpg, 76.37 US mpg).
For a complete list of 2011 records, please visit 2011 Guinness Records in Croatia.