My check engine light went on about a month ago and I got the code read. I had a misfire in cylinders 1 and 4. I went online and found it was the most false given code so I decided to disconnect the battery and turn it off. About a week later it came back on so i thought i should get a full diagnostic on the car. They told me they could find nothing wrong with it and told me to drive it for 3-5 days and see if it goes back on. They also told me if it does go back on to bring it back and they'll change some spark plugs. It went back on when I started the car last night. I was wondering if it would just be easier to replace the spark plugs myself than to pay someone to do it (if so could you please recommend some spark plugs).
Also I've noticed that the engine light goes on EVERY time i put a new tank of gas in. I have an 03 GT and I've been using Premium gas and I wasn't sure if that could cause the check engine light to go on.