Re economy of TDI.
My first trip was Sydney to Melbourne (with approx 200 km on odo, literally brand new, was only a couple of days after I got it) - got about 7.0 l/100km with the 'green'/new engine.
Return to Sydney got 6.5 l/100km.
Going at the the legal limit (110 km/hr, full load of 5 people + luggage and other junk), with air-con running non-stop and doing the right foot varying of engine speed (to run it in) and a fairly regular (every 30 min or so) semi-hard (2/3 throttle) acceleration from 70-80 km/hr upwards . . .
Then did Sydney to Brisbane - got economy of 6.0 l/100km.
On way back from Brisbane, got 5.8 l/100km.
Next did a run to Adelaide and economy was floating around the 6.0 l/km mark . . . did try to stick to the limit/s 
The bad side, on way back from Adelaide (just after leaving Wagga) collected a small 'roo with the left headlight (messy, confined to the light and bumper area; engine, suspension and rest of car was OK). Car is back with me (2 months later - bonnet availability and faulty bi-xenon issues from VW which took a while to sort out, my insurance was great!, rental car I had was cr-p in comparison to the Passat!, ended up with the repair place having car longer than I did since new - I admit that they did a great job fixing it back to like new).
Most recent drive (today, approx 340 km) - MFD showed economy of 5.8 l/100km - mainly freeway driving (110 km/hr zone, cruise control, moderate load, air-con, with full throttle accels every now and again), Newcastle and back. Along with about 220 km of city driving (which showed 7.6 l/100km average on the MFD) in the last 2 days (from full tank), the MFD now shows that I have about 530 km cruising range left from my tank.
Car has just over 9,000 km on it at present (3.5 months since I got it, just over 5 weeks of driving it and 8 weeks at the repairers!).
My observation: I get about 7-8 l/100 km driving in the city (stop-start traffic) and out of the city it ranges from <5.5 through 6.5+ l/100 km (easy 100-110 km/hr cruise control flat run through some 'fun' drives with extensive use of full throttle accelerations - pulls pretty well!).
If I cruise at 100km/hr or lower on the flat, I can easily get below 5.0 l/100km. If I cruise at a steady 60 km/hr on the flat, the instant consumption is hovering around 3.0-3.5 l/100km (think I would go insane if I was to drive at that speed interstate with everyone doing twice that).
Bottom line: You will see an improvement in economy over time.
If you are doing only city driving then you should not be worried about what you are seeing now (8+ l/100km). If you want to see good economy take it for a run on the freeway and see what it gives you economy wise.
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