I just got one of the last G6 sedans, a "new 2009" model. I was happy to find this forum when considering my purchase.
I went looking for info about a cabin air filter, which my last two Fords have had. My search brought me eventually to a Saturn Aura forum which discussed the existence of a place to put a filter, though it does not come with one:
I pulled down my glovebox in one minute -- look closely into the left and right edges, and you'll see the two stops to know just where to squeeze the box sidewalls. The directions there mention a cable release, but my G6 does not have this. The air intake area is right there. Molded into the plastic are some dashed lines and a note - cut here for air filter.
Some of the latest posts suggest that some might have found a premade filter to fit this opening, but it's not confirmed yet. Others went for a DIY solution, like post #50:
Went to Lowe's big box store. Looked at all furnace filters. Selected the following:
Filtrete Ultra Allergen 10 X 20 X 1
-Cut the length to 8" using heavy shop scissors.
This yielded a piece with actual dimensions of:
9 3/4 wide
Nice snug fit side-to-side and top to bottom.
Turned blower on, worked great and I could smell the fresh filtered air!
I'm just going to make my own, I think. After I get the filter in, I will seal it off with a piece of aluminum foil tape. (They say that duct tape isn't really good for ducts, and to use that foil tape instead.) It makes sense to me to seal it back up so that it's pulling only fresh air from outside. The recirc button is what you use if you don't want outside air.