A tiny instrument symbol is proving to generate an increasing amount of interest as  the test mileage grows on our  A3 e-tron. Designed to switch on only to show that the car’s petrol engine is in action, it remains out of sight for at least 25 miles after  a full charge of the battery pack, which is what you’d expect in a vehicle that also has an  electric motor.

But what is surprising is the amount of time the symbol also remains hidden from view  once the initial charge has been used up. After appearing as the engine takes over from the electric motor, it vanishes each time clever gadgetry reclaims power. This happens when pressure is eased on the accelerator to put the transmission into coast mode, during overrun on gentle motorway slopes, when driving  downhill and every time the brakes are applied.

Each of these actions combine to reclaim a useful amount of energy. Experience so far is suggesting the ‘every little helps’ mantra is making for worthwhile savings and as the test approaches the 3,000-mile mark, the car’s average return is on the better side of 60mpg

Another surprise is the silky smooth transmission.