Not long ago it seemed at the very least unlikely that a family-sized car could possibly have official CO2 emissions of less than 100g/km. Such things are still a rarity today, but they do exist, and Renault is one of the manufacturers who provides one.The Megane hatchback fitted with the long-established 110bhp 1.5-litre dCi turbo diesel engine is rated at 90g/km - or, at least, it is if it also has a manual gearbox. The version we're reviewing here falls some way short, since its the alternative six-speed automatic transmission increases its CO2 emissions on the EU cycle to 110g/km.This isn't as big a deal as it might seem. Being on the "wrong" side of the 100g/km threshold, this Megane obliges its driver to pay the London congestion charge, but that won't affect you unless you live outside the zone and don't take your car into it. And, while there's no getting round the fact that this car isn't exempt from Vehicle Excise Duty, as the manual is, the £20 you have to pay in tax is small beer compared with the £625 extra required for the automatic box.That in itself is a modest premium for this kind of transmission, so it would be wrong to expect great things here. This auto, like other units of its type, can be reluctant to change gear in the first few minutes after a cold start, and the shifts are sometimes jerky when the car is moving slowly. These are mild complaints, though, and there's certainly nothing to complain about on the open road, where one gear is replaced by the next very smoothly.The steering is smooth, too, which helps the Megane to regain refinement points lost elsewhere. I have always liked Renault's little 1.5 diesel, particularly in this application where it has just as much power as required and not a bhp more, but it's been around for a long time and sounds rough compared with many more modern engines, even when fully warmed-up.Road noise isn't well-suppressed, either, which suggests that the Megane has been built down to a price. That impression is enhanced by the interior, which in the usual Renault way is rather dull, though the instruments - all digital except the revcounter, and easy to read - jazz the place up quite a bit.Nobody should have a problem making themselves comfortable up front, where there's plenty of space, but the rear is very tight for taller fellows. In my usual "sitting behind myself" test, which involves getting in behind the driver's seat when it's set up in the position I like it, I could squeeze myself into position with a bit of grumbling and cursing, but I wouldn't have wanted to be a rear passenger for so much as a yard unless someone very much smaller were driving.More attention seems to have been paid to luggage-carrying. The rear sill is several inches higher than the boot floor (why do so many manufacturers do that with their hatchbacks and then get the job right with their estates?) but the boot itself is splendidly roomy. It offers more space than those of both the Ford Focus and Vauxhall Astra with the rear seats in place and more than the Focus with the rear seats folded, though all are beaten by the Korean Hyundai i30 and Kia cee'd.Minor storage spaces included lidded compartments hidden under the mats ahead of the front seats. Somebody in the Renault design department must have been having a good day when that was thought up, but such cleverness does not extend through the rest of the car. Notably, there's only one cupholder up front, and there is so little clearance above it that putting an open drinks can in or out carries the risk of spillage.This is one of only two automatics in the Megane range. The other uses the same engine but is in the lower Expression+ trim level. The Dynamique TomTom costs £1000 more, and for that you get quite a lot of extra equipment including air-conditioning, front foglights, automatic headlights and wipers, Bluetooth connectivity, a USB connection, front foglights, a height-adjustable front passenger seat, 60/40 split rear seats, LED daytime running lights, keyless entry and Carminat TomTom satellite navigation. Engine 1461cc, 4 cylinders Power 110bhp Transmission 6-speed automatic Fuel/CO2 67.3mpg / 110g/km Acceleration 0-62mph: 11.7 seconds Top speed 118mph Price £20,425 Details correct at publication date