How do I burn an audio cd which will play in my car from a cd with mp3 files?

I have a cd containing 29 mp3 files that will not work in my car. Therefore, I'm trying to convert them to an audio cd format that will work in my car and burn them to new cd. My question is 3 fold...1) what file formats work in a stereo (cda?, wav?; I've read some say wav will and some say wav won't work); 2) how come all 29 mp3 files on my existing disc takes up about 550 MB but when I go to burn it as an audio cd I can only burn 2 of the files (the files are only 8MB but about 35 min in length) before it says the disc is full (I'm trying to burn it to a 700MB/80Min cd)? I understand more than 2 files of this length would exceed the 80 Min requirement but why was this not exceeded on the mp3 cd (it was also a 700MB/80Min cd)?