The guy at the Fred Meyer in Wasilla who told me my car was fine, then said something I still think about
Last October I was loading groceries in the parking lot off the Parks Highway when an older guy in a Carhartt jacket nodded at my rusty Subaru and said "that thing will outlive us both, you know." I laughed and said it barely starts below zero, and he just shrugged and told me his old truck ran for 19 years on nothing but oil changes and stubbornness. Then he said "everything up here is just a race against the salt" and walked off to his rig before I could ask what he meant. So what is the actual lifespan of a car up here before the frame turns to lace?
How old is your Subaru? I ask because I went through this same thing with my 2004 Forester. The salt is the real killer up here, not the cold, and once it gets into the rear wheel wells and the subframe it's pretty much over no matter how good the engine runs. What worked for me was crawling under there every fall before the first snow and spraying the frame and rocker panels with fluid film, plus hitting the car wash on warm days in the middle of winter to knock the brine off. Mine made it to 240k miles before the rear strut towers got soft enough that my mechanic told me to stop driving it. I'd say 12 to 15 years is realistic here if you stay on top of the underside, and the guy was right that it's a race, just not one you can ever win.