BMW has published further details of its upcoming 1-Series EfficientDynamics Edition, which will be the most frugal car in BMW’s line-up when it goes on sale in March.

The most important piece of new information is the price – the 116d ED will start from £20,885 on the road, a £380 increase over the ordinary 116d SE on which it’s based.

Although the EfficientDynamics Edition has a smaller diesel engine (it gets a 1.6, whereas the regular 116d is actually a 2.0-litre), weight remains unchanged at 1,385kg, while power and torque remain pegged at 116bhp and 260Nm respectively. The figures underscore how modular and software-controlled engines have become these days, with outputs governed more by economics than by engineering.

The standard 116d is not exactly profligate – all new 1-Series cars come with a wide range of fuel-saving technologies including stop-start and part-time ancillaries - helping to achieve a 117g/km CO2 score. But the EfficientDynamics Edition does better at just 99g/km, due to a 10mm suspension drop, low rolling-resistance tyres and slightly longer gearing in its rear differential.

That all-important under-100 rating means the EfficientDynamics Edition can slip into the London congestion zone free of charge, while company car drivers face only a 13% benefit-in-kind tax rate, the lowest bracket possible for a diesel car (upcoming hybrid diesels aside).

BMW’s fuel miser can whistle to 62mph in 10.5 seconds, just a couple of tenths slower than the ordinary 116d due mostly to the longer gearing. It sits on 16-inch alloy wheels and comes with a six-speed manual gearbox. Standard equipment includes Bluetooth hands-free compatibility, a USB audio interface, front foglamps, a multifunction leather steering wheel, a 6.5-inch central display and iDrive controller.

BMW is keen to point out that its car betters the rival A3 1.6 TDI Sportback on a range of measures from performance to emissions, but so it should – the BMW is still a wide-eyed and fresh-faced young model, whereas the A3 is just a few months away from retirement. It must also be noted that the BMW is about 800 quid more expensive that the equivalent A3.

Superiority might not be as clear-cut as BMW would suggest, but the EfficientDynamics Edition will no doubt be a good car, and all the better for being so economical.