Aha! What a bunch of bull! For the price in simeoleons it should clean itself by default, not to mention that you'll be forced to make a sim in the household have a mechanic skill. Is it also unbreakable then? I can comfirm that I had a sim upgraded it and it does clean itself after the upgrade.
After the my sim upgraded it to clean itself, it also got clogged! It plays the music and cleans itself though.