How would I know if I got bad gas

How can you tell if you have gotten bad gasoline or if there is something else wrong with your car? My car cut off as I was turning into a store parking lot. And when I tried to re-start it, it makes horrible sounds when it's running and then cuts off a Lately the car has been having a strong burnt smell after cutting it off. When it died at the store, I had smoke coming out from under the hood. I had spilled oil under there the week before, and also it had been raining a lot. My oil was okay, and added water to the radiator overflow container. Even though car was no showing running hot. It was sort of in between hot and cold. When I go to start it back, it runs but cuts back off, after sounding all sputtery and knocky.