My car kept dying when I stopped, then started making weird noise & now won't start? Oil light is on?

It 0 degrees where I live, & I only bought the car 4 months ago. It is a 99 ford taurus, I bought it for 800 on craiglist. I brought a mechanic with me to check it out n he saw no other problems besides a small antifreeze leak and the gas gauge being broken.
I'm not out of gas, I filled up today. I could start the car a couple hours ago, but it died whenever I slowed down and at every red light. I finally got it home and as I was pulling in, it died again, and when I tried to turn it on it made a different noise and wouldn't start for longer than 2 seconds before the oil light goes on and I can't press the break down. The engine also started making some sort of knocking noise out of nowhere as of yesterday.I'm having a friend mechanic come look at it but he isn't off work for two more hours. What could this be?

The oil pressure light is on because it's not running - that's normal under these circumstances. It's possible you have moisture in your fuel - you could try some dry gas additive. This is often a problem when it gets this cold. Beyond that your mechanic will have to figure it out.

Tiffany, correct me if I'm wrong but I doubt that you are the kind of girl who will put on a pair of coveralls and crawl under a car with a set of wrenches in her hand. Given that, there's nothing you can do to fix this. This is almost certainly not the kind of problem that can be fixed by dumping a bottle of stuff into the gas tank or oil.

You need a mechanic. It could be any number of things - throttle position sensor, crank angle sensor, MAF sensor, a bad alternator, a bad fuel pump, a clogged fuel filter, etc… You need a good mechanic - emphasis on good.

Let me tell you a very bad habit of "shade tree mechanics" and bad professional mechanics:
The take a guess buy a part and install it. When that doesn't work, they take another guess, buy another part and install it. When this doesn't work… You get where I'm going with this? This is called "throwing parts at a problem."

Do not buy any parts unless your mechanic can prove to you that the old part has been tested and has proven to be defective. I'm trying to save you money here.