Well, this cold weather is really hard on vehicles so it is hard to say, especially since you would seem to have multiple issues. IMHO top it off with 5W-30, and take the battery out and fully charge it. Then go back during the day so it is warmer and you can see. Anyway, I have a feeling your alternator might be going bad. I’d be breaking out a voltmeter if I were you. And if your losing a quart (or more) a week, I’d try to address that soon as well. Assuming it is not to late already.