Fluids

Keep it simple! Look at the trans dip stick. If the fluid is pink or nearly clear light brown, it's ok. If gray or black then simply drain it and refill with 3.75 qts ATF. If still black after a day's driving repeat. FLUSHING the system involves BACK-flushing, which introduces great risk of sending dirt up through the sensitive valves. DON'T DO IT! Lots of shops like to sell flushes because they bought computerized equipment that back-flushes it automatically while they have lunch, picking up egregious fees for this dangerous service. Think of the transmission fluids as like in a digestive system...you NEVER want to push it up backwards!

Skip the flush and do a fluid change.

If your Subaru says to use premium gas, do it. You are not saving yourself any money w/ cheaper gas. It will burn faster and you will hurt to many other things along the way. It was actually meant to run on better gas and uses it more efficiently. I tried the mid grade for some time and wish I had not. Just don't do it.

Huh? You're on the wrong thread. As well, NO Outbacks require 89, 91 nor 93 octane. Fed 87 is just fine.