redav 5pts The problem with the diesel is related to capturing unburned hydrocarbons for emissions. If the car is driven too often for short trips where the oil doesn't get up to temperature or if the engine shuts off during a re-injection cycle, it can find its way into the crankcase oil. Pretty much every modern diesel with these filters are susceptible, not just Mazdas. The problem essentially comes down to this: If you drive a lot of short trips, you need to follow a stricter maintenance schedule of checking oil more often and getting it changed if the level rises too much. (If that is too difficult for you, you should not buy any diesel.) If you normally drive longer distances, a less strict maintenance schedule can be followed with less frequent oil changes.