Road Test: Renault Megane 2.0 dCi 175 Renaultsport 5dr

So you've just bought yourself a Megane dCi 175. Your wife/husband/partner/bank manager phones up, demanding to know why the bloody hell you blew all that hard-earned cash without consulting her/him/anyone first.

Here's the thing. You can justify your purchase. You highlight the 175's economy (43.5mpg), cheapish insurance (Group 12) and - importantly in these dark days of Gordon's war on CO² - low emissions. You make a cogent, sensible case and hang up the phone with a smug look on your face.

And that's the problem. See, Renault is touting the 175 as its first-ever diesel hot hatch. Not just as a quick diesel, but explicitly a hot hatch. And, in my book at least, you don't just buy a hot hatch because it's sensible.

Sure, it's more a concession to real-world concerns than, say, an Ariel Atom or a Shire horse. But a proper hot hatch should, at least in part, feel like a guilty pleasure, a triumph of "oh, go on then" over "but I really shouldn't".

Yet the 175 never engages enough that you'd buy one on the spot and to hell with Jimmy's tuition fees.

Not that it's anything but a deeply competent car. The chassis, particularly the Cup version, is lithe and responsive, and the traction control is brilliant, even by Renaultsport's own high standards.

The 175 isn't slow, either. The 2.0-litre turbodiesel, transplanted from the Laguna GT, is deceptively rapid. Renault says the 175 will outpace a Megane 225 between 50 and 75mph in fourth gear, and while that might reek of selective statistic-grabbing, it's a fair measure of the torque available. It doesn't arrive in one tumescent surge, either - the boost is progressive and spread right across the power band.

But it's quiet. Eerily quiet.

When I asked Renaultsport's Stephen Marvin about the 175's muted tones, he said that the engineers had made a conscious decision to keep the noise down, sacrificing aural engagement in favour of motorway comfort. "And besides," he said, "it's tricky to get a decent engine noise from a diesel four-pot."

Sensible, yes, but sensible shouldn't be in the hot hatch lexicon. If Renault had taken the 175 and slapped it around a bit - loosened a few screws, insulted its parentage - it could have been brilliant. As it is, the 175 is a fine, grown-up car.

But it's no hot hatch.