Volkswagen Group reported Thursday that European sales of its core VW brand cars jumped by a staggering 30 percent in July to 163,000 units. The Wolfsburg-based auto manufacturer said the success was largely due to "special sales initiatives for cars approved under the outgoing NEFZ test procedure.

Those cars can currently be bought at a discount and can no longer be sold come September this year. The company increased its VW sales in its home market by 33 percent.

Worldwide, a total of 505,900 VW cars left the showrooms in July, making it the best ever month for the company's core brand in terms of sales.

Slump ahead?

VW sales chief Jürgen Stackmann warned, though, that due to a new certification procedure starting in September the company would have to grapple with some bottlenecks and face more stoppages until October.

With the switch to the new Worldwide Harmonized Light Vehicle Test Procedure (WLTP), Volkswagen and others are facing major challenges.

"Within the VW brand alone, we need to test more than 200 model variants and have them type-approved within a very short space of time," CEO Herbert Diess said in a recent statement.

"Many vehicles will have to be warehoused in the meantime, and we will have to plan closure days through the end of September."

The WLTP test procedure is much more complex and takes much longer, with the volume of testing work three to four times higher than was previously the case.

VW works council chief Bernd Osterloh said the company had failed to install a sufficient number of testing rigs to deal with the job properly.

hg/tr (Reuters, dpa)