Yes it is illegal. The answer to the original post. Great though reading all the previous posts. The manufacturers get their vehicles to euro 5 standards by fitting dpf's, cats,EGR and the like. I wonder what tests are done to get euro 5. It is only when the real driving begins with the normal punter do we see the inadequacies of the dpf. Some but certainly not all manufacturers have done a good job. So where does that leave the customer. A rock and a hard place springs to mind. Until they get it more reliable it is going to be a problem. I think the legislators are pushing too fast and reliable technology can't keep up. Companies spending thousands on equipment to service DPF's tells it's own story.
Regards to all
Les