More Car Problems

1. The leaks aren't over.  Since I've gotten it back I have seen what appear to be fresh spots on the driveway.  They weren't as big as they once were before I brought my car in ... until a few days ago, when what looked like a sizable (I've been using the word "sizable" a lot lately) spot of oil greeted me when I left in the morning.  The mechanic thought he got everything, but there was one trouble spot underneath the hood he chalked up to dirt, and he decided to just clean it up.  But now that it seems that it really is a leak.  He knows.  At least he knows.  Paying him to fix it, well, that's another matter.
2. One of the tail lights is burnt out, according to my instrument cluster.  No big deal; I've fixed it before. In fact, it might be the same light.  All I have to do is get the right bolt and unscrew four bolts.  Just have to remember which four so I waste my time or pull out the wrong thing.
3. The cold weather probably/might be the reason the automatic lock on the driver's-side door does not open when I use the button on the driver's-side door or manually turn the lock on the passenger's-side door (although it works fine if I stick my key in the driver's-side door).  Usually in extreme weather (more in the summer than in the winter, however) it's the passenger's-side door lock that won't open remotely.  Now that works fine by my door doesn't.
4. Oh, and the oil level light is coming on again.  Not really lately, but off-and-on the past couple weeks. I thought that with the engine "fixed" the oil would stay in the engine, therefore I wouldn't need to fill it up so much.  But I've put in a bottle-and-a-half last week.  It's holding, for now.  Then again, maybe the oil leaks I still see on the driveway are an indication of where the oil is going.
5. ETA: I forgot the bad new thing: I saw a new rust spot on the car.  And it's a place I wouldn't expect: On the surface, thigh level, just behind the rear driver's-side door.  Noticed it a few days ago.  How could that be?  There's a hole in the underside of the car, right underneath the driver's-side door, but I understand that because that's where snow and salt collects.  But right on the side like that?  Moreover, from the bubbling underneath the paint I can detect surrounding this spot, there probably is more, a lot more.  How long can I keep this car?