Porsche could be given a substantial fine by the German government after admitting that fuel consumption and emission figures submitted for type approval of the outgoing 991-series 911 were incorrect.

The fuel consumption and emission data submitted to the German Transport Ministry prior to the granting of type approval for unspecified 911 models in 2016 and 2017 included incorrect values due to miscalculations in their drag co-efficient. According to a report by German newspaper Der Spiegel, Porsche self-reported the error to German authorities and is also set to inform US authorities.

Der Spiegel reported that laboratory tests carried out on the old 911 failed to factor in the drag co-efficient, which led to figures that do not represent real world fuel consumption and emissions.

Fuel consumption and emission values gained on a rolling road are much lower from those in the real world owing to a lack of wind resistance. The error means that the affected 911 models use more fuel and emit more emissions than noted in their type approval.

Porsche chairman Oliver Blume says he has informed the German Transport Ministry of the false data and Porsche engineers are now reportedly working with German government authorities to determine the extent of the miscalculation.

Under German law car makers can be fined if fuel consumption and emissions vary by more than 10 per cent from their claimed values, and customers could also claim compensation. It is not yet know how much variation there is between the figures Porsche recorded, or how many cars are affected.

Autocar has contacted Porsche for comment, and is waiting for a reply.

There is no indication of any mistake in data submitted for the recently launched eighth-generation 911.

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