I bought mine used at 112k miles and it burned oil then, and got worse as time went on. It was a persistent misfire and low compression that moved me to replace the engine with one out of a 2016 Forester.Did it burn oil from the beginning, or come on with some decent amount of miles. Maybe the oil control rings get gummed up from poor design (lacking good drain holes in the oil ring groove) and something like Valvoline Restore and Protect could help clean up the ring pack.
But a lot of them burned oil in excessive amounts since day one. It was a mechanical defect, not something any oil would have fixed.