I actually know exactly what you mean. I work at a movie theatre and open tubes of brand new posters fresh of the presses almost every day. You can always smell it. It's a little like vinyl.
I wonder if I could smell it on an eight year old poster, however.
I am still a poster newb but I am thinking If the poster is unused, brand new and coming out if its original home it will keep that new car smell for a few years.