It has been sitting on my shelf for 3 years......in the basement.
It's my fault it's rusty, I'm not trying to call STP out.
It's just surface rust on the metal, no big chunks are going to fall off, but there may be some small rust bits that fall out, hopefully the filter would catch this?
It's just surface rust, right? You should be able to just rub it off. One of the best ways to get it off would actually be to use some of your old/used oil and a rag. I used to do that at work when I'd come across an older filter that had been sitting for awhile. Just got some oil on a rag and scrubbed it off.
STP oil filters are cheap. Buy a new one. I could see if it was a European or Japanese-made filter, or a Wix, or a US-made K&N, because those filters are good and could be hard to find, but an STP, not worth it.
I have a couple of M1 filters made in 2008, and they look brand new, and even the box does, too.
Get a Napa Silver/ProSelect, Carquest Red, or Microgard.
Really? For less than $4, you're willing to possibly risk damage to your engine? If there is rust you CAN see on the filter, then how much is INSIDE the filter that you CANNOT see?
Go spend the $4 and get a new filter. Don't take the chance.
If anything, cut the rusty filter open and post pics of it on here.