A couple of months ago my iPod touch stopped holding a charge and I didn't want to spend very much on a replacement. I found out that the car stereo can use an USB stick for playback and I have a few kicking around so I filled a 8GB USB 2.0 and I was good.

I recently bought a 64GB USB 3.0 and loaded 34GB of music in MP3 format to it, but when I went to use it in the car there were playback issues and when I went to 'Browse' the unit by Artist, Album, Songs etc. it just kept searching or reading all the data and I finally gave up after 20 min drive waiting for the stereo to get all the information. Come to find out the stereo isn't USB 3.0 friendly. I've also tried a 64GB USB 2.0 with about 34GB of data and still the same issue but it did find first folder and played a song.

I'm still testing the 64GB USB 2.0 but I'm removing more songs and will test it at 24GB of data. I'm looking for that happy medium where searching the data doesn't take anymore than a minute or two. I'll keep dropping the amount of sons till I do and report back.

The manual for the car states I can have much more but does not indicate the issues in searching the data for playback as stated below...

The manual specs state this:

USB memory ●Compatible devices USB memory device that can be used for MP3, WMA and AAC playback. ●Compatible device formats The following device format can be used: • USB communication format: USB2.0 HS (480 Mbps) and FS (12 Mbps) • File system format: FAT16/32 (Windows) • Correspondence class: Mass storage class MP3, WMA and AAC files written to a device with any format other than those listed above may not play correctly, and their file names and folder names may not be displayed correctly. Items related to standards and limitations are as follows: • Maximum directory hierarchy: 8 levels • Maximum number of folders in a device: 3000 (including the root) • Maximum number of files in a device: 9999 • Maximum number of files per folder: 255 ●MP3, WMA and AAC files MP3 (MPEG Audio LAYER 3) is a standard audio compression format. Files can be compressed to approximately 1/10 of their original size using MP3 compression. WMA (Windows Media Audio) is a Microsoft audio compression format. This format compresses audio data to a size smaller than that of the MP3 format. AAC is short for Advanced Audio Coding and refers to an audio compression technology standard used with MPEG2 and MPEG4. MP3, WMA and AAC file and media/formats compatibility are limited.

Update from Jan 9, 2019: The next day I took the USB 2.0 64GB stick with 24GB of data, but I also removed all playlist (.M3U8 or .M3U) and folder cover images to reduce the amount of files being scanned by the car stereo. (Great program to copy just .mp3 or any file extension you want is called 'Beyond Compare')

Having removed everything from the folders except for the music, the stereo took approx. 4-5min to scan the 24GB and the ONLY place you have the 'Random' option is when searching by 'Song' and not available for Artist or Album. If you choose these then choose folder by folder until you get to the songs available. So, to make the search take less time you would have to reduce the amount songs. * SPECIAL NOTE - The Song Random option has to be picked every time you restart the car if you don't wish to locked into the last song played album and from there it will just play that album.

The manual also states this:

File names The only files that can be recognized as MP3/WMA/AAC and played are those with the extension .mp3, .wma or .m4a. Extensions If the file extensions .mp3, .wma and .m4a are used for files other than MP3, WMA and AAC files, they will be skipped (not played). ●Playback • To play MP3 files with steady sound quality, we recommend a fixed bit rate of at least 128 kbps and a sampling frequency of 44.1 kHz.