I actually had the 235/60r18 GO15's and the hit to gas mileage was insane, Thankfully Discount Tire took them back. They were simply to much tire for the car.And that's 5 lbs per tire over stock with the 235/60/18 being 9 lbs over stock. The GO15 in 225/60/18 seems to be the "lightweight" A/T choice at 29 lbs per tire.
I actually just found out this morning that they now make the GO15 in 225/60r18. I'm sure they would be a much better fit for an outback or than the 235's but i don't know how much. They are a legit AT tire and the more capable off-road an AT tire is the mmore rolling resistance / bigger hit to MPG you will take on road.
I'm just happy to see some decent , and light weight, AT tires being made for crossovers now. In my opinion that's all you need for the newer gen outbacks and foresters. If you need a lift the bigger tires then you simply have the wrong car.
I didn't realize that i was posting in the Gen 6 forums. I have 2017 outback and everything i have said in this post and the previous ones is from my experience with that car and not the newer 6th gen.