There's a part of this comment which makes me think I'm missing something. According to their website, the Mercedes A180 CDI ECO gets 78.5mpg.

78.5.

I own a car I would consider sporty, and I can still get over 35mpg when driving on motorways at a sensible speed.

I'm in the UK. Are we using some other metric to establish MPG or are cars in the USA really that absurd that they get your quoted 25mpg on a long journey?