STUTTGART, Germany - Mercedes-Benz has launched its first nine-speed automatic transmission, the 9G-Tronic, in the E350 BlueTEC, now set to become one of the most fuel-efficient six-cylinder diesel cars in its class.The patented transmission design and efficiency has reduced the fuel consumption in the E-Class to 5.3 litres/100km and 5.5 litres/100km on sedans and estate models respectively. The new gearbox is available as standard and is ready to order from showroom floors at no extra costs to customers.IMAGE GALLERYIn the E350 BlueTEC, the V6 diesel engine makes 185kW and 138g/km (Estate 144g/km) of CO2 emissions thanks to the extra gear and the broader ratio spread.Mercedes says the overall reduction in engine speed makes things quieter to the tune of four decibels. The broad ratio spread enables, Mercedes says, "a clearly perceptible reduction in engine speed and is a decisive factor behind the high level of energy efficiency and ride comfort". The automaker adds that shorter shift and reaction times ensures spontaneity combined with ease of shifting. In manual and "S" modes the gearbox responds more spontaneously.Together with the extended gear-ratio spread, higher road speeds can now be acheived at lower engine speeds - 120km/h in ninth gear requires only 1350rpm.SAME SIZE, LIGHTERThough it has two extra gears and can handle as much as 1000Nm the gearbox takes up the same space in the engine bay but is lighter. The two-piece housing has been retained: the torque converter housing is aluminium, the transmission housing is plastic and the sump is made of an even lighter magnesium alloy.Mercedes also tried to achieve a minimal number of planetary gear sets and shift elements, the result being a total of four sets and six elements. This is achieved using three speed sensors to monitor operation and provide the transmission control system with corresponding data for effective shifting. Several gears can be jumped when accelerating or decelerating, should the driving conditions allow it.The new gearbox is also fitted with two pumps: a considerably smaller mechanical main pump, featuring an off-axis design located next to the main shaft and it is chain-driven and fed by a separate electric auxiliary pump. This also enables the benefit of stop/start technology. The 9G-Tronic transmission will be implemented in other model series and engines with rear-wheel, all-wheel drives and also hybrid and plug-in hybrid drive systems under the German stable.The European market launch will be in September 2013.