would it be correct to use(s) in the following scenerio?

There are two car air fresheners that someone has left on a table. Would it be correct to leave a note next to the air fresheners that reads : Put in your car(s)? Each person only has one car.

the sense would be clear which ever you used. Since, in English, there is no difference between the plural and singular form of "you" I would say that either would be fine, and not sound odd, as it might in a language where there is more pronoun variation,
(and more stress about "agreements"!)
You only use ( s ) to make things plural when quantity is unclear. Since you know that everyone has only one car, you do not use ( s ).


If one person owns one car and one person owns two cars, you could use ( s ) since you don't know who will read the note first.
 suzi's reply was promoted to an answer.