Stop-start local E stopped - for the moment

Mercedes-Benz will offer a stop-start version of its new W212 E-Class in Europe next month but it will be at least two years before the fuel-saving feature arrives Down Under in Benz's premium large exec models.

Just launched in Spain and set to go on sale in Germany this month with a 40,000-strong order bank, the new E-Class boasts significant fuel economy improvements across key models.

Thanks to new engines, a range of improvements lumped under Benz's BlueEfficiency banner (more here) and a body that Mercedes claims makes the new E the world's most aerodynamically efficient luxury saloon (at a Cd of 0.25 it matches the new Prius!), the W212 posts fuel economy improvements of up to 23 per cent when compared to comparable W211 models.

By way of example, the new 150kW/500Nm 2.1-litre twin-turbo diesel E 250 CDI model coming Down Under boasts combined cycle fuel economy of just 5.3L/100km. Frugal new turbocharged direct-injected petrol four-cylinder models are also featured in the international W212 line-up.

It's one of the latter, the E 200 CGI that introduces automatic stop-start into a Benz sedan for the first time. But before any local greenies with a bent for luxury get too excited, the bad news is the car's not coming Down Under.

Currently Benz offers the auto stop-start system with the six-speed manual version of the turbo-four 200 only. At this point, larger petrol engines, Benz's four-cylinder turbodiesels and all automatic transmission equipped models are off limits for the stop-start system.

Based on normal city traffic conditions, Mercedes says the system can cut fuel usage by as much as 10-12 per cent. Savings across the official Euro combined cycle are more modest -- around 4 per cent, says Mercedes-Benz engineer and stop-start expert, Dr Hartung Wilstermann.

Wilstermann says the company is working towards fitting stop-start to a wider range of models. He says the system is designed to provide fuel economy benefits across a range of engine sizes without the expense of a full hybrid-style drivetrain, but as such has some compromises. For example, the stop-start function is disabled until the car warms and when high loads are placed upon the car's aircon and other systems.

Nonetheless, Wilstermann says the way the system 'grades' user's aircon and other energy requirements would be 'robust' enough to cope with real world use in Australia's climate. Unlike some other stop-start set-ups, the Mercedes system can be disabled by choice by the driver.

E-Class vehicle durability and development testing head, Joachim Lindau, suggested the company is well advanced with testing the stop-start system on automatic models and on more powerful engine variants.

Though neither Wilstermann nor Lindau would be drawn on specific timetables, both suggested more stop-start models, including variants more commonly seen in markets like the USA and Australia, would be launched "soon."

It's likely such models will hit the market alongside the diesel-hybrid version of the E-Class tipped to debut in 2010. That would indicate an introduction Down Under of the stop-start models at least by early 2011.

Look out for our full international launch review of the new Mercedes-Benz E-Class here soon.