ULEZ:
Benzinfahrzeuge der Schadstoffklassen Euro 0 – 3 und
Dieselfahrzeuge Euro 0 – 5 erfüllen nicht die Anforderungen.

Edit:

The £12.50 charge applies 24 hours a day every day of the year except Christmas Day (25 December).[14] The criteria for charging is based on European emission standards:
Motorbikes that do not meet Euro 3 standards (most vehicles pre-2007)
Petrol cars and vans that do not meet Euro 4 standards (most vehicles pre-2006)
Diesel cars and vans that do not meet Euro 6 standards (most vehicles pre-2015)