It's all down to your mileage and how and where you drive. If you're mostly in town and only driving short hops then you're going to develop problems with your diesel particulate filter (DPF), which needs the heat generated by longer, faster journeys to clear itself out. You can get around that by making sure you go for a good, long blast up the motorway (at least 50km above 100km/h), but that might not be convenient for your schedule. 

 

However, I have some good news. The 08/09 Mazda6 also came with a choice of 1.8 or 2.0 petrol engines so it might be worth your while tracking one of those down, as they may be much more suited to your driving profile than a diesel.