I have an older Ford (2002) and Ive found the biggest issue with discs for me tends to be ISO issues when disc is setup
The Mach MP3 players tend to flip out over naming issues, too many files in a directory, weird characters (eg burn a Jpop or Kpop song and filenames cant be read) etc etc

Bitrates and CBR/VBR issues tend not to pop up so often in my experiance

My player also hates RW media... Im not sure why but...