Transmission ratios are playing an increasingly important role in the motor industry’s quest to wring the most from every gallon.

But driving can be a chore when manufacturers specify ratios so high that anything but cruising on flat and open motorways calls for constant use of the gear lever.

Happily, that doesn’t seem to be the case with our long-term Renault Megane Sport Tourer, because even though it mates a modest-output engine with a six-speed gearbox featuring one of the ‘tallest’ ratios available, the car is surprisingly good to drive.

Of course, the unit in question is the 1.5-litre dCi, the best-seller that went under the bonnets of 1.2 million Renault models last year and now, following a thorough engineering makeover, has also been adopted by Mercedes-Benz for the new A-Class.

Geared so highly that the speedometer needle reads 37mph with the engine spinning at just 1,000 revs in top – that’s little more than idle speed - you’d be forgiven for thinking this Megane is a sluggard for most of the time.

But you’d be wrong. Even though it has only 110bhp on tap, the revamped unit behaves in a lively fashion as long as it is kept spinning over the 1,500 revs mark to get the full benefit of turbo boost.

After more than 10,000 miles of driving, I’ve had plenty of time to appreciate the finesse of the latest dCi unit and understand why it was chosen to power a car produced by one of the world’s best-known premium manufacturers. The smoothest of operators, it makes little noise and remains largely inaudible for most of the time, being particularly relaxed and restful over the long journeys for which it is ideally suited.

And for good measure, fuel economy continues to impress, with a general average of 60mpg.