My wife bought her 2015 MKC used in 2015.
I noticed a hint of smoke smell when we test drove and she didn't.
I brought it up on that drive, then she did smell it, but figured we could get rid of it.
We cleaned (everything), shampooed, and sprayed Ozium all up in that car.
It helped a little.
Being her car is garage kept, she left the windows down at night and we left a fan running into the car.
After about 3 weeks the smell subsided.
But if the car sat in the heat for an extended period of time, a hint of cigarette smoke lingered inside for 3 years until she traded it in on her SRX.
We tried an Ionizer and it didn't do sh!t.
Change the cabin filter, if it has one, spray some Ozium on it.
The smoke is embedded in the carpet, seat foam rubber/leather, the headliner, the door panels, etc...
We found you can weaken the smell, but you'll never completely get rid of it...