Hi We are currently almost in a done deal with a 2008 S320 CDI, which has a DPF, however before putting the payment down we just want some last minute advise on this topic. i checked with my local indie, and he told me about these additive type products, which aid the regen process, he said go for a motorway run once a month and add this additive (such as forte dpf cleaner) to the tank once a month also and you should be fine with you're everyday city driving type runs. i would like to know what is you're take on this? do these additives really work, and is this scheme of city driving + motorway run once a month + additive formula reliable enough? because the car would mainly be used for city stop and go short trips type driving. also could you please explain what is actually a good motorway run for reliable regen to take place, how long?, what speed?, non stop? etc advise would be much appreciated, as the car is great, it is only this DPF issue which is a bit doubtfull.