Both Mercedes-Benz parent Daimler and Volkswagen Group have approved new plans to retrofit older diesel-powered vehicles with new software at no cost to owners.
The largest number of such cars will be in Europe.
The news comes amid the latest allegations surrounding German automakers and their brands' diesel cars—and more updates could be on the horizon.
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BMW has also committed to a voluntary program to retrofit older cars, though it has outright denied any wrongdoing on the topic of European diesel emission standards.
Audi's announcement applies to 850,000 cars worldwide with 6- and 8-cylinder diesel engines. The brand says the updated software will not only curb real-world emissions, it will help cars do better than the current legal requirements.
Audi will have a watchdog peering over its shoulder, however: Germany's Federal Motor Transport Authority, known as the KBA, will oversee the software implementations and work with Audi during the process.
2014 Mercedes-Benz E250 BlueTec 4Matic
Volkswagen Group's luxury marque remains under investigation by the KBA after the Audi A8 was outed as a potential emission cheater in Europe.
Daimler's voluntary program has been expanded to three million cars in an effort to cut emission outputs from older diesel-powered cars.
The automaker says it will incorporate its most advanced technology from the latest family of diesel engines in the software update to ensure a cleaner burn.
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Like Audi, the KBA will also be working side-by-side as Mercedes-Benz outfits older cars with the latest software.
Authorities won't simply be observing this latest diesel update initiative, though—there may be worse things for the makers on the horizon.
Last week, the European Union confirmed it was investigating BMW, Audi, and Mercedes-Benz over alleged collusion to rig diesel emission standards in Europe.
2014 Mercedes-Benz M-Class (ML350 BlueTEC)
The three German brands are said to have worked together since the 1990s on procedures to "circumnavigate" diesel emission regulations.
Up to 200 employees and closed-door meetings attended by representatives of each marque led to shared information over various ways to manipulate software.
At the moment, these accusations are not fact, but it may only be the beginning of Europe's diesel deceit.
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While BMW has yet to announce plans for a similar program, it did release a strongly worded statement surrounding the allegations.
The automaker denied it had any part in the manipulation of its diesel-vehicle software to cheat emission tests.
It also strongly defended its current diesel technology, saying there is "no need to recall or upgrade the software of BMW Group Euro 6 diesel passenger cars."
2014 BMW 328d xDrive Sports Wagon
2014 BMW 328d xDrive Sports Wagon
Should the EU's allegations prove true, each automaker could be slapped with major fines—Volkswagen Group has stated costs surrounding its diesel emission scandal have topped $25 billion.
That's largely made up of the North American settlements, buybacks, and modifications.
Costs from European countries and other markets have yet to be fully understood.