Just curios. If you think this is a silly question I apologize. The Manuel for my M&Ps does not mention oiling the recoil spring, BUT I have oiled my recoil springs in the past without issues.
I did some more digging and this seems oddly different from person to person…
I very lightly oil my recoil spring guide rods. Made a noteable difference in spring compression action. Lighter and not gritty as when dry. Been doing it for quite a while and it hasn’t been a problem.
I clean my recoil spring with solvent but I have put a drop of oil on it and it didn’t do any harm.
Recoil spring doesn’t need to be oiled for functionality.
However - whenever you use cleaning solvent on spring or rod - they have to be wiped with touch of oil, otherwise they are completely dry. (No need if you use CLP.)
Once you put a little oil, just wiped it out with dry cloth or patch. More oil on spring means more residue to clean next time.
Yeah… First advice -don’t take the baby to the Range 
I have found brown gunk in my recoil spring. I was advised by Craig in another post it was probably grease or Lacquer for long term storage. I have read more online and found a few people with the same issue.
S&W actually sent me a new recoil spring, but I would like to quality test it to assure it works before I carry with a new spring Any advice? Not sure if I should just throw in the new spring and be happy, leave it alone till I get to the range (Not sure when that will happen) or try to clean it out more. Here’s the gunk pics.
That was a huge hic-up on my part… 
@Scoutbob,
Use the old one before you get a chance to test a replacement. I know manufacturer says it’s ready to go… but this is matter of life or death, there is no place for trust. Test first, use later.
If you find the replacement working good, no need to keep old one. Perhaps only if you want to play with it, disassemble and clean. But is it worthy?
That’s what I’ll do, thank you!
I very lightly oil the spring and guide rod. There’s no method to my madness, my logic is … the firearm is apart, it’s dirty, I clean it and lube it.
That’s a well used looking weapon. In the picture it looks like wear and patches of rust to me, but if you say it’s more like varnish, I believe you.
Could it be a heat varnish from lots of rounds in short order cooking whatever solvent or oil was left on the spring?
