It’s taken less than three years for stop-start technology to win a front-line role in the battle to cut tailpipe emission levels.

But will the gadgetry that saves fuel by stopping engines when they’re not needed and firing them up again automatically prove to be reliable in the long term?

The question is prompted by the on-off behaviour of the system fitted to our long term Vauxhall Insignia: it was on for 2,600 miles but then turned itself off and remained dormant during the three days it took to drive a further 600 miles.

Over the considerable distance the car has covered in the meantime, the equipment has failed to operate on three more occasions but has come back to life after only relatively short periods, adding further to the mystery of its on-off behaviour.

For all that, the Insignia is putting in a sterling performance in every other respect and is turning out to be a star act when it comes to operating efficiency.

Backed by a generous tank capacity, the car’s ability to return regular consumption figures on the better side of 50mpg makes it ideal for drivers who need to cover long distances without the penalty of wasting valuable time on service station forecourts and the higher gearing that comes with the ecoFLEX packaging gives our model a particularly relaxed cruising gait to make light of motorway mile munching.

The relatively generous specification that comes with the Exclusiv trim level also provides all the conveniences that help cut the stress of long periods at the wheel.

With stretching room for its occupants, this is comfortable transport indeed and I’m impressed that it’s possible to adjust the height of the driver’s seat and change the level of lumbar support by pressing a couple of buttons - an unexpected touch of luxury in this class of car.

By Maurice Glover