I’m 90 % sure it’s gum. It’s been on the passenger floormat for probably 4 months & is dried out. A friend must have inadvertently stepped on some gum before stepping into my car. It’s noticeable, as it’s whitish in color against a tan-colored carpeted mat.
In the old days we used to use carbon tetrachloride to remove such problems as gum or the tar that you always used to pick up at the beach. I don’t think you can buy carbon tet any more because of EPA regulations.
Other strong degreasing compounds that you may have would wreak havoc with the carpet’s rubber backing. I suggest you take the floormat to your local dry cleaners for a professional opinion.
Acetone will remove gum.
…and dissolve the synthetic fibers in carpeting, right? My experiences with acetone were that there were only a select few plastics it did not immediately attack.
Along the lines of carbon tetrachloride, Brakleen brake cleaner (the one in the red can) is 100% tetrachloroethylene per the MSDS (less a small amount of CO2 as a propellant). That’s dry cleaning fluid.
I’ve used acetone and never had a problem with it. Like many other chemicals it should always be tested in an out of sight area first. I’ve also used aerosol carburetor cleaner to do the same thing and never a problem with that either.
Put the floor mat in the freezer for a good long time. The gum will get very hard and most of it can be chipped/scraped off. Repeat until you get it all. If you end up getting to where you get most of but just have a little left I’d move on to a mild solvent like goo gone. But freezing & cracking should get most of it.
Put the floor mat in the freezer for a good long time. or get some dry ice.