"We would like to save gas, but we are not allowed to, due to emission protection regulations," Martin Daum told the newspaper on Thursday.

"We're discussing shower temperatures and whether we should stop lighting monuments: That's an absolute joke compared to what we could save as an industry if we could unbureaucratically and quickly convert our heating plants to heating oil," he said.

Daimler Truck has been in the position to switch all its process heat to fuel oil since the end of July to early August, which would save about 40 gigawatt hours of gas per month, he said.

However, to do so requires going through several layers of government and seeking expert opinions, he said. The German lower house of parliament is expected to decide in late September or early October whether to shorten the process.

"Sometime in late October we may be allowed to switch over," he told the newspaper.

(Writing by Miranda Murray, editing by Rachel More)