Bakerman

As a later poster said I think it is more to your driving style than the economy of the car (and that is not a dig), Bora diesels (VW in general) in particular can be very very frugal. You do need to adjust your driving style just like Plato has had to adjust his racing a diesel, recently I went from Oxford to Stratford on a mix of A and B roads and averaged mid 60s, OK I wasn't flying along nor was I holding anybody up but still enjoyed attaining that economy.
All about low revs, getting into the higher gears asap and momentum if you can be bothered .............

Blueblaster

Hairy muff . Why not try 60mph for one tank of petrol? Nothing to lose, but maybe something to gain? You're almost at the limit of your potential savings, but I think you just need a little push to help you achieve the Blueblaster level of anality.

Ringpeas

I got 45 mpg on a long mixed run in a VAG 1.8 petrol turbo, just by driving sensibly and using the brakes less.
People seem to be looking at extremes here by comparing an STi to a modern TDi
I think you need to compare a petrol and deisel model of the same type of car.

Blueblaster

Very true...however, if you look at the mpgs that magazines get for their long term cars it is very common to see sub 25mpg and sub 20mpg is not unusual. I think the fact that you are driving a diesel can change your mindset away from maximum attack to steady progress. I suppose it is fair to say that buying a petrol hot/warm hatch or something similar and then driving it economically rather defeats the point and will still cost you a lot more in tax and insurance.

Fuzz

If you can get your brain past the "I must have a better car than the neighbour" then a small car, small diesel engined **** box is where it's at. (If you really want / have to cut the bills in half)
Pittance to purchase, parts are cheap, road fund is cheap, insurance is pocket change, tyres are peanuts and best of all it does 60 to the gallon.

Beat the hell out of running a classic Impreza that had the requirement to modify it every week and that did about 6 to the gallon every time you put your foot down and of course in a car like that you had to use the loud pedal on every occasion.

Dieseldog

Good 'real world' mpg's for all sorts of cars can be found at Spritmonitor.de. Germans love keeping records of their fuel consumption and here they list them, some going back years. You need to register and change your preferences to see mpg's as opposed to litres per 100km's (the Euro standard), and then take a sensible view and discount the extremes but you get a better idea than the manufacturers' figures.

Personally I genuinely get 60mpg from the station car - an old 90bhp Golf TDi, but that is driven with the idea to keep costs as low as possible.