Mazda CX-5: Diesel oil dilution

When I bought may Mazda CX-5 diesel last March I was concerned to find a brochure inserted in the car's manual stressing the need to check the oil level every 1000 km, or monthly, and to have the oil changed if it rose to a level marked on the dip stick above the "Full" level mark, as failure to do so could result in substantial damage to the motor. The insert was obviously an afterthought as there is no mention of this requirement in the manual, except for the usual advice to check the oil level as a normal part of regular checking of the car's fluid levels. Apparently diesel fuel is forced through the diesel particulate filter to clean it and this fuel ends up in the oil. During the first 10,000 km the oil level did rise, but did not get to the danger level. Since that service the car has done just over 3000 km and the oil level has increased to the danger level and I have had to have the oil changed. The 3000 km was a mix of long (400 km) drives and shorter drives (50-100 km) and running to work (15 km) and a few trips to the shops. This was all country driving, not stop/start city driving. The inconvenience of needing to have the oil changed every three to four thousand kilometres is one thing, but the cost involved is quite another. It is going to be an expensive car to maintain and the issue must surely have an adverse effect on the resale value of the car. I hope you may be able to give me and other CX-5 owners some more information on this matter.