Subject: Why is petroleum a polymer, while gasoline is not?

I work for a Museum that teaches a lot of chemistry-related 
workshops.  We have a poster that we often use in our polymer 
discussions that lists a number of polymers.  The poster lists 
petroleum as a polymer, and makes a side note that "gasoline, 
however is not a polymer".  During a recent workshop, an adult 
questioned the poster, saying if you don't count gasoline as a 
polymer, then petroleum isn't one either.  I know that gasoline 
and refined petroleum both undergo hydrocarbon cracking to break 
down the carbon molecules into smaller pieces that help prevent 
knocking and generally make engines run more smoothly, and I 
believe that explains why gasoline isn't considered a polymer.  I 
had assumed that our poster was referring to crude petroleum, and 
that once refined, it was broken down (like gasoline) and was no 
longer considered a polymer.  But while researching further, I 
discovered that petroleum is generally only comprised of chains 
C6 to C20, which seems too short for a polymer.  Is petroleum 
then really a polymer, or is our poster incorrect?  And if it is 
considered a polymer when it only contains C6 to C20, then why 
isn't gasoline 

Re: Why is petroleum a polymer, while gasoline is not?