Flac is a lossless format that would be wasted on Car stereos. The gain in sound quality in a Car would get drowned out by road noise, so for in the Car, MP3 will do. VLC media player should be able to convert flac to mp3 for you. Sorry, have to go...

Edit: I'm back. Alright then, here we go. In the world of digital sound there are enormous quality differences, and this is not a matter of view, rather a matter of fact. Analog sound comes at you in full format, everything, every bit of information is present. To digitize it all so it can be processed by a dumb machine, it is chopped into little blocks of information. Flac has a lot of little blocks in it's box, which makes for a rather large file to keep in storage.

MP3 tries to store what can be compared to a single picture, rather than record and store every pixel, it tries to store a photograph. In sound that means that anything that is barely audible will no longer be present in an MP3 file, making it much smaller but sacrificing detail that an audiophile craves.

Cars are a noisy environment so MP3 is fine as even the audiophile would not hear the difference. If he/she does you don't want him/her on the road because he/she has no time for traffic.

Here is a matter of strong views: Disco sucks! Unfortunately those with strong views miss out on a lot of good stuff. Take for example the excellent rhythm guitar work of Nile Rogers (Chic) offset by a piano that says as much by not playing certain things as it does with the notes that some times come out seemingly random. Delicious!

Hope you find and read this edit. I'll try to stay up late....