To bloom in the world of TopGear, an eco car must: a) drive you to somewhere far-flung on a single tank of fuel, and b) make you smile goofily on the way. This new Polo Bluemotion will, unfortunately, only manage the first of these.
The trick to a car like this is finding a sweet spot between efficiency and driveability. With stats of 83.1mpg and 90g/km CO2, the Polo does a fine job of the economy thing, but wrecks all that good work with an utterly turgid driving experience.
But before we get to that, let's look at the tech. This is the second-gen Polo Bluemotion and features an all-new 1.2-litre three-cylinder diesel. It uses regenerative braking and stop/start for the first time in a Polo, all of which edge the mpg figures into the magic 80s and keep CO2 output in that all-important tax-free band.
The engine is more than a remapped jobbie. It's been made with mpg in mind and - as friction is the enemy of efficiency - many parts, such as the crankshaft, valves and oil pump have been smoothed and improved to reduce resistance and so burn less fuel. To maximise all that mechanical slickness, the gear ratios have been made longer so the engine runs at a more efficient speed for more of the time. That's not unusual in an eco car, but the VW engineers clearly suffered a spot of overkill.
So for the first few thousand revs in the Polo, it feels like you're driving through thick sludge. You can complete a long and creative yawn in the time it takes to get through a gear, before a dash icon lights up and encourages a shift up. But obey that, and you'll bog down in the next gear and end up jockeying the seat, willing the car to get a bloody move on. It really is rowing-boat slow.
But it doesn't have to be like this. In the Fiesta Econetic - the Polo's nemesis - there's still fun to be had, with a tight chassis, lively steering and a 1.6-litre diesel that successfully juggles a neat whack of power with 76.3mpg economy.
Of course, strip away the Bluemotion stickers, and you still get a refined, well-made and good-looking car - a Golf-lite, perhaps. But you're always aware that this is an eco car and that the dull drive is a pay-off for those headline figures.
In the pursuit of absolute efficiency, the Bluemotion is still a saintly thing, glowing like a halo above VW's fat corporate head. But for those of us who like cars with a bit more sparkle, the day you actually desire one is the day you should put down TopGear magazine and buy a copy of Bowls International.