My commute is 115km round trip in rural Ireland. I leave for work very early so roads are very quiet. I don’t hang around by any stretch and my average is 40mpg easily over the contents of a tank. 700km from a tank is no problem. It’s all about the journey. When my wife takes the car in and around town she struggles to see 30mpg. Anyway, it’s a GTi so economy doesn’t matter.
Ps my car is tuned to 305bhp and only other mods are pedalbox and Sachs upgraded clutch.