Mercedes-Benz has added a new nine-speed automatic into its line-up as standard equipment on the E350 BlueTec.

The new in-house-produced unit, known internally under the name 9G-Tronic, has long been mooted for selected Mercedes-Benz models.

However, its existence was officially denied until the weekend, when Mercedes-Benz’s German language website configurator went live with various updates for the E-class line-up – including an entry signalling the 9G-Tronic is now available on the standard rear-wheel-drive E350 BlueTec in place of the older seven-speed 7G-Tronic automatic gearbox.

The adoption of the 9G-Tronic fails to make any impact on the official E350 BlueTec’s 0-62mph acceleration, which remains at 6.6sec. But with two extra ratios and improvements to its stop/start function over the 7G-Tronic unit, its combined-cycle fuel economy figure has improved from 51.4mpg to 53.3mpg, according to Mercedes-Benz’s own figures. At the same time, average CO2 emissions have been lowered from 144g/km to 138g/km.

The moderate improvement comes through a more than nine per cent gain in city cycle economy, which improves from an earlier 40.9mpg to 44.1mpg. The motorway figure remains the same at 60.1mpg.

The new gearbox is suitable for both four- and rear-wheel drive applications as well as hybrid and plug-in hybrid models. Mercedes says the gearbox will be available in "almost all model series and engines in the coming years."

In other changes to the E-class line-up, Mercedes-Benz has introduced the seven-speed 7G-Tronic automatic gearbox as standard equipment on the E220 BlueEfficiency Edition. Previously, it came with a standard six-speed manual gearbox.

In saloon guise it retains the same 0-62mph acceleration as the earlier E220 BlueEfficiency Edition with the then optional seven-speed automatic, but its combined-cycle consumption improves from 60.1mpg to 64.2mpg, reducing average CO2 emissions from 132g/km to just 114g/km. Autocar understands the upgraded model now also complies to EU6 emission regulations.  

A new E200 NGD model has also been introduced. The natural gas-fuelled E-class runs the same turbocharged 2.0-litre four-cylinder engine used in the B200 NGD, with 154bhp and 199lb ft of torque. Mercedes-Benz claims a 0-62mph time of 10.4sec and combined cycle economy of 4.3kg/62miles – the equivalent of 44.8mpg.

The gearbox will be available as an option in the UK from 2014.