This is the facelifted Mercedes B-class. Set to make its public debut at the Leipzig motor show on 4 April. It's underneath the skin where the new B-class receives most of its developments.The 1.5 and 1.7-litre four-cylinder petrol engines, and both the 109bhp and 140bhp 2.0-litre diesels have been reworked to produce a seven per cent reduction in fuel consumption, and lower CO2 emissions. Additionally, buyers will be able to specify a stop/start function on the petrol B150 and B170 BlueEFFICIENCY models. Styling changes are subtle, to say the least, with a more wedge shaped front bumper, bolder grille, more heavily creased bonnet and new exterior mirrors providing the biggest visual clues. Changes at the rear are even less marked, with lightly altered tail lamp lenses and a new bumper for easier access. Another new arrival to the B-class line-up is the B170 NGT (natural gas technology). It is based around the 115bhp 1.7-litre four-cylinder B170, which has been adapted to run on either petrol or natural gas. In addition to the standard 54-litre petrol tank, it also houses five separate tanks capable of stowing up to 16kg of natural gas. Drivers can switch between petrol and gas modes via a button on the steering wheel. Tank levels are shown on an LED display.With official consumption figures of 38.7mpg in petrol mode and 57.7mpg in gas mode, the B170 NGT possesses a theoretical range of up to 620 miles – some 186 miles on gas alone. CO2 emissions, meanwhile, are claimed to be up to 17 per cent lower than the standard B170 at 135g/km. Mercedes has withdrawn plans to sell the B200 and B200 Turbo in the UK when the facelifted B-class arrives here in July. A company source said that “demand for the higher performance models has not met initial targets and they will not be part of the future line-up sold here.”Sales of the B-class have never really taken off in the UK, but it has been a hit in other European countries since its launch in 2005. Sales to date total 325,000 – enough to convince Mercedes to begin development of a second-generation model. Due out in 2011, it is set to grow slightly in dimensions to a size similar to the Ford C-Max, Volkswagen Touran and Vauxhall Zafira.