Mine was squeaking too so I pulled it out and vacuumed it up and lubed it and it stopped squeaking. There were definitely some leaves in there. While I was at it I installed a cabin air filter so that I wouldn't have to worry about leaves any more.
I used tri flow lube for it because that is what I had around and I use it on bikes to good effect. Pretty much any good lube will work (WD40 is not a lubricant).