Seems like my head gasket leak is getting worse. I've known I had a leak for more than a year, but I've just been ignoring it and adding coolant regularly.
I've never overheated the car, so I kept wondering why/where it was leaking. Think I finally got a clue yesterday.
When I had the radiator open topping it off, there was a grey residue around the filler cap and in the overflow bottle. Seems like it might be aluminum... might have been having an electrolysis problem this whole time.
I probably would have changed my coolant more regularly, but I'd always thought I was going to swap the engine out at some point, and just never have made or had the time or set aside the money. Now I'm debating about what to do.