Audi tops BMW and Mercedes in luxury sales

It's not all good news, though. Audi's worldwide sales only jumped by 2.5 percent, compared to BMW and Mercedes, whose sales increased 5.6 and 11 percent, respectively. On top of that, BMW is still the best-selling brand (of the three, anyway) so far in 2015, outselling Audi by roughly 9,000 units and Mercedes by about 23,000 vehicles.
Considering the faster growth of its rivals, it's unclear if Audi will be able to hang onto the monthly sales crown beyond April, or if BMW will continue its reign as the world's biggest luxury automaker. Source