Subaru Forester 2013: Is it using too much oil?

I have a 2013 Subaru Forester 2.5S. It has done 80,000 km in 5 1/2 years, and has been serviced as per the Service Log Book. Since approx. the 20,000 km mark the engine has been using a lot of oil. The low oil indicator light comes on around 5000 km after it has been serviced.
I get the car serviced by Subaru and they have noted it, but say this is "acceptable oil usage". The Subaru Service Dept. said if oil was required at 3000 km or below that would be an issue. There are no oil leaks as Subaru tested the car for me … again. It is frustrating as the car is great except for the high oil usage. I top it up with the Subaru recommended oil each time. Is this a normal or acceptable thing for this type of vehicle? Have you had other people raise this with you? What can be done to prevent this?