Okay so on a recent road trip in my '94 Pontiac Grand Prix I got fuel at a truck stop and noticed that my car was acting different than usual. I kind of ignored it (it was the middle of the night and I just wanted to get to where I was going). The next day the starter was totally dead on my car so I replaced it. But when I start it my car (if you're sitting in the driver seat) is like.. shaking. I got AWFUL mileage for a good chunk of the way home (down to 15 mph from 24) and every now and then when I press my gas pedal the shaking gets harder. My dad things it could be a motor mount (Because my engine is shaking) but my grandfather thinks its my fuel filters. Any suggestions?