I have a 3DS XL and my slide pad has more resistance than it should. (I have a New 2DS XL to compare it to by the way) I let my little sister play it for awhile and when I got it back, the slide pad wasn't gliding around too easily. Maybe she got food in there. I can fix it by rubbing a damp cloth under all sides of it. This fixes it for like a day but it goes back to the usual high resistance after that.

I want to sell it to offset the cost of buying the New 2DS XL but I don't feel right telling someone "It works great except you have to wipe down the slide pad every so often."

What are my options? Would a little bit of non-organic oil under the pad work or do I need to send this into Nintendo and have them look at it? That's the last thing I want to do though.

Nintendo will charge you 125 to replace that circle pad, or you can follow a teardown guide and replace it yourself. I think you can buy a new stick for $5, or you may get away with simply cleaning it.

It really sounds like there is some sugar under there that is sitting in there as a thick syrup. Popsicles, soda, OJ, and candy will do that. It would also free up temporarily when you add water if it were sugar, as sugar will disolve in to water. Problem is, you cant remove the sugar and it just dries out again- and this is why I suggest tearing down the 3ds, so you can possibly clean it out of there. You wont need a cleaner, only water.

You dont want to put oils in it, organic or not, because the oil will travel and you will short out your 3DS. You also dont want to keep putting water in there, as it could cause corrosion or shorting.

@yabbering_yeti:Thanks. I found this guide: https://www.ifixit.com/Guide/Nintendo+3DS+XL+Circle+Pad+Replacement/25074

Sugar makes a lot of sense.