There may be a few things at play here — first of all, DVD and CD are very different types of media, so if your car player only handles CDs, then a DVD would just be unreadable, period. You also have to be sure your car player can handle the format you’re trying to put onto that disc — there are players that will specifically handle discs with MP3 on them, but most of them still only handle discs encoded as audio CDs.

If you’re doing all of this properly, there’s also the possibility that your car’s player simply doesn’t like home-burned media: recordable discs typically have a different luminance than factory-pressed CDs, which means that you can’t play them in the car even if they might work in another player in the home. You can try a different brand of media, or even switching to a CD-RW instead of a CD-R.