What kind of brake fluid should I use for a 2005 Chevy Cobalt Coupe Ls?

[milla_meta]

How much do I put in? The light has come on three times since I got it in July. The first time, my cousin put brake fluid in, not sure how much or what kind, and the light went off for a month or two. Then it came on again, and I was sure it shouldn't have come on so soon. So I took it to the dealership, they did an inspection, and found no leaks or problems. Now, after about a month and a half it has come on again, and seems to come on more often than in the past. Is there a problem?
I went to wal mart and bought brake fluid that is made for both DOT 3 and 4.
I'm not sure what all of this means, so I would like to know if I bought the right kind, and if not, I can return it and get what I do need.
Thanks so much!

 

[Gene S]

Use Dot 3. If you are adding brake fluid, you do have a leak. Brake fluid will not evaporate. Have it checked remove all wheels. Check every line it has to be leaking somewhere. Check master cylinder, could have a seal bad and sucking fluid into vacuum chamber and than burning the fluid in the engine, which would be my quess if no external leak. Have check ASAP it is a dangerous thing to have a brake leak you never know when you will not have brakes.