That sounds about correct for mine. 2003 2.5 TDI SWB.

 

I get around 30-35 mpg, but I live in North Wales, and mostly do short journeys up and down hills. Mine is 2.5tdi 88hp, with intercooler and pp0.5s

 

https://www.vwt4forum.co.uk/showthread.php?t=150058

put another way - how many miles on a tank ? IIRC 80L tank, so should easily get > 600 (34 mpg) on a run and even > 700 should be poss (40 mpg), maybe even 800 is just poss if on an economy drive !! and no load in van, with a tail wind, all downhill (so JoGLE not LEJoG !) etc etc