Ok so I have read lots on the forum regarding which oil is best for an A3 2.0TDI 170. Some are saying 5w30 and some are saying 5w40. I have come down to two choices either the Shell Helix Ultra Extra 05w30 or what seems to be a new oil, Shell Helix Diesel Ultra 05w40. The diesel branded oil has various comments on cleaning the engine of soot and reducing sludge ect. I cant find any info on this forum regarding the diesel oil either. Has anyone had any experience with this Shell diesel oil? I presume the engine will also be quieter on 05w40? Can anyone say why one oil would be better than the other and for what reasons? My car has done 62000 its been on long life services but I intend to do a yearly service. I cover 10-12k a year but 90% of it is town driving.