Volkswagen has said it may have to refit up to 11 million cars and vans worldwide, and new CEO Matthias Mueller said in a newspaper interview on Wednesday recalls would start in January and would be completed by the end of 2016.
But owners are anxious to know whether the refits will affect the fuel-economy and performance of their vehicles.
Volkswagen has said the illegal software was not activated on the bulk of the 11 million vehicles, most of which are in Europe, leaving uncertainty over whether it rigged tests there.
The German transport ministry has said it did manipulate European tests too, but has not given details, making it unclear whether the company faces the same level of fines and lawsuits in Europe as in the United States. It is also unclear whether owners will be obliged to have their vehicles refitted.
Equinet analysts said the cost of refits could range from less than 100 euros ($112) per vehicle to as much as 10,000 euros, depending on whether Volkswagen needs to upgrade software or install new hardware.
UBS analysts estimated the total bill for the scandal, including potential fines and lawsuits, could be around 35 billion euros, though they also noted this was more than factored into the company's share price after its recent plunge.