i live in the extended ulez zone, and my brother recently bought a 2004 volvo c70 2.0t, so i had to look into this recently.
ulez is focused on NOx emissions. that is, 0.08 grams per km is the ulez limit.
ALL euro 4 cars have to meet the nox limit of 0.08g/km, thats why the 2005/euro4 rule is...