Write about a car you especially loved or remember. Include details, tangible or intangible, that will help the reader to see what it means to you.
OR write an amalgamation of all the cars you've loved -- do a smash up, bang up job, tossing all their best aspects together into one awesome ride.
It doesn't have to be a car of yours, it can be the car of a friend, a family member, or one that you worshipped from afar.
Shoot for a length of between 350 and 500 words.