In my experience it is not just a case of what goes into the engine ( ie clean fuel that is able to be well filtered . meaning regular filter changes ) but what comes OUT. These things are not commuter friendly in that the auto seeks to be in the highest gear possible to keep revs low and assist fuel consumption but that means the engine and exhaust rarely gets really usably hot. Notice how long it takes for the OIL gauge to reach operating temperature. It is a lot longer than the water temp. A forced regeneration makes the entire exhaust system and the DPF get really hot and burn off the accumulated deposits. It is designed to do so. In my case I had stupidly dosed the fuel with a diesel injector cleaner and went to Europe for a while, as the result I suspect some chemical cleaning occurred .. and when pressed back into service after standing for a couple of months several "depollution system faulty" messages appeared over the following weeks until the car could be given a good hard hot run. The old fashioned "Italian tune up" cured the "commuter blues". My son was running a Mitsubishi Colt Ralliart at the time, and the multi brand service dealer was also the local Peugeot service centre. Discussion with the tech people revealed many of their Peugeot customers cars were not getting through new car service intervals without needing the diesel fuel filters replaced. They of course were blaming the fuel supply at the pumps, but I suspect it was equally the style of commuter usage that is not suited to diesel engines no matter how physically and chemically strangled the exhaust system may be to appease the Euro 3,4,5,6 legislation. Note the evolution to AdBlu systems that only appeared in the very last of the C5s.
The HDI engine really likes a good hard hot cleaning run, the sort that used to make exhaust pipe deposits white back in the days of leaded petrol.