The more I think about it the more I am convinced it was the KTS. The vehicle kept logging a fault code for DPF regeneration which returned seconds after clearing. What ever varient of engine ECU I choose showed the oil dilution % and then carried on to reset it to 0%. Have a play and I'm sure you'll find it.

Also found this while searching when I had this fault. May help if you're working on a 6.

http://www.cdn.dk/mazda6/tips.htm

Matt