Yup, never do such favours for people.
"My engine exploded after you changed the oil".
That would be my worry, hopefully the husband sees all this and gets it.
But i don't get the " I don't know, its my wifes car" I'm not chauvinist, but i make sure all the vehicles in my household are maintained, not just " mine" I bet there's other problems there.
I don't understand people. You spend 30k plus on a new car and don't think about taking care of it. Dude needs to exchange his man card for a snow flake card.
If she was leasing the car that makes sense (not really).
While I don't do it myself and wouldn't tell anyone else to do it, 12k miles on a synthetic oil probably isn't much of a concern.
A 2015 Subaru Crosstrek owner on another forum changes his oil every 12,000 miles with Mobil 1 0W20 and now has 970,000 miles on the car. The FB20 engine was swapped at 634,000 miles. Speaking of oil changes and Subaru Crosstrek owners.