The mileage of the Volkswagen CC on our long-term test fleet has fairly shot up in recent weeks, and a surprising number of those miles have been covered in neutral (or something approximating it).

That’s because the CC’s dual-clutch gearbox has a fuel-saving coasting function – a feature that’s found on an increasing number of DSG-equipped diesel-engined Volkswagens. It’s an interesting development (at least, it is to me), and one that’s worthy of some discussion. So here goes.

The coasting function declutches the engine when the throttle is lifted, which means that the car is free from the momentum-hungry shackles of engine braking (such as it is with a modern common-rail diesel) on the overrun. Now, before you write in and say that today’s engines have an overrun fuel cut-off which shuts off the fuel supply on a closed throttle, and that an engine coasting on tickover with the gearbox disengaged actually uses more fuel than one coasting in gear on a closed throttle, well, apparently it doesn’t.

In short, when you lift off you end up travelling much farther before you have to get back on it, and the subsequent fuel savings outweigh whatever is burnt on tickover while coasting. Touch the throttle or brake while coasting, or move the gear selector from D to its manual shift position, and the gear re-engages. The coasting function can also be disabled via the onboard menu settings, or overridden by keeping manual control over the gearchanges.