Vrrrrrrrrroooooooom. You can write about the pro's and con's of different car's and compare them to each other.
How about suggesting to your websites visitors the ideal car for those on a strict budget.
Give a history of the automobile with such facts as: when the first car was made, who created it, what gave them the idea to create it.
Give driving tips for all the bad drivers.
A daily car joke.
Just do you.