Here's a little update, since our CX5 was having the dilution problem for the first couple years. Very noticeable in winter, warm weather driving was not a problem.
About a year ago, I was on the last attempt at a fix and left the car with the dealer. FWIW, it had been in there several times for the same problem. Anyways, this time they did a bunch of ECM/ECU updates, and surprise surprise, the problem seems to be fixed. Just completed an oil change at 8000 kms, November > May, so running the entire winter. I checked it a couple times during that period and the level did not fluctuate. Took out 5L and dumped a 5L jug back in.
A couple other noticeable things......the exhaust tips were always covered with soot. Since that repair, they are clean as a whistle, the inside of the pipe is shiney spotless. Car runs great, excellent fuel mileage, good throttle response, runs better than ever since we bought it new.
Thanks for reporting.