2015 Subaru Legacy 3.6R engine knock and burning oil

We purchased my wife’s 2015 Legacy 3.6R about
6 months ago. We purchased the car some 400
miles from home, and when we stopped to get gas
on the way home, I heard a pretty aggressive
engine knock. I used to own a 14 Legacy and it
made some strange noises, though proved
extremely reliable. I summed it up to that.

Well, my cusrioaity got the best of me and when I
took it to the dealership for a few small warranty
concerns, they told me that the knock might be
from the previous owner cold starting it and just
throwing it in gear and going, but nothing to be
concerned about.

Now, about 2,000 miles into my most recent ok
change, my low oil light came on. I checked for
leaks, nothing. I checked the oil and it was
EXTREMELY LOW, like the dipstick didn’t have a
drop of oil on it. I filled it up with FOUR QUARTS
and it seemed fine. I took it back to a dealership
and they said the compression looks good and
there are no leaks. “Don’t worry about it.”

My wife works nights and has a short, 10 mile
commute, I don’t drive he car often.

My questions are as follows: how can I solve this
tremendous oil burning? Whats the cause? Does it
have to do with the Engine knock? I know that
these boxers burn up oil, but this is out of hand.