Change in tempo after audio mixdown??

Gday all.

I just did a quick audio mixdown to mp3 to listen to a song in the car on may way home from work just for reference. I noticed an obvious difference in tempo on playback and obviously pitch as well. Not chipmunk style but it did sound faster and the end time of the song on my car stereo was earlier that that on Cubase by about 10 seconds.
Just wondering WTF? Is this a result of compression (neewbie question perhaps) or a setting in Cubase that I have missed.

Appreciate any help.


As in all the other posts with the same problem - it’s certainly a samplerate problem.