said by EUS:Older guy I know recently bought a golf tdi, claims to get over 1000km/tank.
You cannot get that mileage with reg fuel engine. I can get (tops) ~500km on a tank with my civic when mostly highway driving.
My Dad drives a '13 Jetta TDI - and 1000k out of a tank is pretty standard for him, as well.
His previous car (also a Jetta TDI) was identical to my mom's Jetta (except hers is a gasser) - and he routinely got 2-300 k more out of a tank then she did.