Hello, I have already Googled with, but unfortunately found nothing suitable. Which exhaust gas filter exists or was there for diesel vehicles between 1990 and today? Can one derive from the pollutant class which filters a vehicle has? Background is the planned purchase of an older diesel vehicle (manufacturer and model is not yet established) in the range of pollutant classes Euro 2 – Euro 4. In the ads only the pollutant class is indicated, but not whether and which exhaust gas cleaning I’ve got a vehicle.