Changing the viscosity a
Changing the viscosity a little will not hurt the engine. When I purchased my 2013 Outback 2.5i Premium in late 2012, the dealer tech(s) told me that the Subaru branded synthetic oil was garbage and that they were using the Toyota branded synthetic oil in the Subarus.
I did some research and made a few calls and found that using a 5W-20 synthetic oil would be fine. Further research yielded the fact that 0W-20 synthetic oil had far more vaporization and burn off than a 5W-20 synthetic motor oil. All other values in terms of viscosity testing, etc. are within a few points of each other (0W-20 versus 5W-20). I am toying with the idea of going to a 5W-30 synthetic in warmer weather.
I have 57.5K miles on my 2013 Outback and change the oil every 4000 miles. Oil consumption is about 0.5 quarts per 3000 miles. I do top off with that 0.5 quart to keep the crankcase full.