Europe's nominee to be climate chief surprised car manufacturers last week by saying she thought EU policymakers might have been too soft on them when carbon-capping rules were set in 2008.
Connie Hedegaard's forceful intervention during hearings for the European Commission raised the possibility of a renewed push by Europe to legislate car emissions if the Dane is approved by the European Parliament for the post next month.
The exisiting rules were hard-fought-over in 2008, with big European auto nations such as France, Italy and Germany arguing that a slow transition to tougher targets was necessary to protect jobs in a sector that is not only one of the EU's biggest employers but already feeling the heat from the economic crisis.
If new emissions caps were brought in, Big Auto and its army of lobbyists would swing back into action, pitting themselves against environmentalists and industries with an interest in tighter curbs, such as car parts suppliers and aluminium producers, who promise to cut the weight of future cars.
Most experts and policymakers think it is unlikely Hedegaard will reopen such an emotive debate to change the 2015 targets for cars, which are now written into law.