My Not So Green Car

I have a 2001 Toyota Corolla. I got it used in 2005 after my 1990 Dodge Colt was proving far more expensive and unreliable than it was worth. My Corolla has just over 108,000 miles on it and it has been an impressively low maintainance car up until now. I have recently discovered that my car has a slow oil leak. After nearly seizing my engine for lack of oil I went to the local auto parts shop and purchased a 5 quart container of the stuff. Then I felt super guilty. A 5 quart container surely uses less plastic than 5 1 quart containers. But isn't what's in the plastic even worse than the plastic itself? I mean...what do we even do with this stuff after we "properly dispose" of it? According to the American Petrolium Institute recycled motor oil can be re-refined into usable motor oil or used by power plants to produce energy. Their oil recycling website makes this all sound very environmentally friendly. It should also be noted that the API website is giving "Hyrdraulic Fracturing", also known as Fracking, a lot of positive attention. So I'm feeling just a little skeptical that we can have our cake and eat it too in this situation. Once the evening rains stop my lovely boyfriend is going to take a look under my hood. We're hoping that it's just a loose oil filter combined with long trips in hot weather that made all my oil disappear.
The oil leak is also making me feel guilty as that oil, distributed all along my driving routes, is probably mucking up wetlands and streams on its way to the ocean right now...I know it's not much oil in the grand scheme but every small amount adds up!
I need a car. Where I live it's just not practical to not have one. The buses only run once an hour and the trip to work, while only a few miles, is very hilly and the roads aren't bike friendly. In the winter it's too cold to wait around outside for a bus or even consider riding a bike anywhere.
I'm hoping that the oil issue is an easily solved one and that it doesn't cost me a fortune. I'd like this car to live at least until 15, like the other one did. If I'm going to own a car I'd like to be as environmentally responsible about it as possible and part of that means not getting a new car unless it's absolutely neccesary. I am lucky that this car hasn't needed lots of new parts and that it is relatively fuel efficient.
Maybe one day I'll live somewhere where cars aren't a neccessity. But probably not, I do love country life.