What I have learnt is we should say "The car is yours" or "The car is your car". Can we ever say "The car is your"?
***** NOT A TEACHER *****
Just remember this, and you will never make a mistake again when using these possessive pronouns.
This car is mine.
This car is yours. (You use "yours" if you are speaking to one person or to two or more persons.)
This car is his.
This car is hers.
This car is ours.
This car is theirs.
Police officer (speaking to Mr. and Mrs. Smith): Is this car yours?
Mrs. Smith: Yes, it's ours. The car is registered in both our names. I insisted on it.
Police officer: Why did you park your car in this prohibited zone?
Mr. Smith: The decision to do so was hers, not mine!
Police Officer: OK, then. The name on the citation for illegal parking will be hers.