Small, specialized sports car makers like Porsche, Ferrari, Maserati, Aston Martin and Bentley, have been concerned with the European Union’s threat to introduce a mandatory limit on fuel consumption, The Detroit News reports.

This would require an average fleet output of about 43 miles per U.S. gallon, although the details of how this would be implemented have yet to be disclosed. But experts say the new CO2 rules would be designed to allow specialist manufacturers like Porsche to demonstrate an annual improvement in CO2 emissions, but not forced down to levels which would threaten its existence.

“Any tax burden or fines (for exceeding CO2 rules) will ultimately be passed down to the customer and with these high end products they won’t be too worried,” said CSM Worldwide’s British-based Europe Sales Forecast Manager, Walt Madeira. “People buying these vehicles don’t have green on their agenda; for every Leonardo DiCaprio, hundreds of others want to buy these cars.”