My ipod mini volume has changed?

I own an ipod mini, and I use the aux in jack in my 2006 scion tc to listen to my mp3's on the road. Recently (2 weeks ago maybe) the max volume got much lower, I have to set the radio volume to 20 as opposed to 15 to achieve the same volume. I haven't made any changes to my car stereo audio settings, nor have I made changes to iTunes or my iPod. Since I own an iPod mini I am under the impression it is older and probably falling apart.