I think it says "Mazda car [something]". I think it might be a service sticker, or maybe a dealership sticker? Mind you this is just from me copy and pasting Katakana characters that look like the ones on the sticker into Google Translate!
I got as far as "マツダカ ート" if you wanted to try - which says "Mazda cart" according to Google Translate. The last two characters I don't have aren't Katakana - I think they are Kanji. But there are thousands of Kanji characters so makes it difficult.
Here is the list of characters I was going from: http://en.wikipedia.org/wiki/Katakana#Table_of_katakana
Take this with a grain of salt 'cos I have no formal education in Japanese - I only know this from trying to decipher Cosmo brochures
Hope that helps,