Club Obi Wan

WD-40?

Really? I'd say stick to Pecards and other leather oils designed specifically for leathers...WD-40 probably could protect your jacket...Probably...But it's not designed for that specifically...And why run that risk?

Essentially...Pecards...

WD-40 does not belong on leather... if you are treating a jacket use leather lotions or oils specifically.
Feel free to use WD-40 on a squeaky door hinge if you like, but lithium grease will do even better long-term on something like that... those types of lubes belong on metal based products.

Also keep in mind, 'WD' stands for 'water displacer'. It's not really a lubricant anyway.

Regards! Michaelson

Learn something every day ...

Short answer:
Don't use it.

Long answer:
I have used WD-40 on a vintage 1930's Archer leather jacket with no ill results (yet). The jacket in question had a very strong mold odor and the sleeve seams were ripping. When all the orthodox methods failed I tried Naphtha and then WD-40. I figured that if it did not work, the jacket was a dumpster fire anyways, so the worst case, I would completely ruin it.

As we know the best conditions for mold are warm, damp and dark environments. As Michaelson said, the WD is water displacement and the 40 is that it was the 40th attempt. We had WD-40 and Kroil in big drums in the maintenance shop where I used to work as an environmental manager. I built a database of all our chemicals in Microsoft Access and had every chemical we had on hand, so naturally, I looked into the safer ones to try on the leather. I skipped past the biocides because they are dangerous to work with. So that left WD-40. In addition to the water displacement, it is a solvent-based penetrant and a lubricant - so I was hoping that it would penetrate deeply into the leather and displace the moisture that the mold needed to survive. I used both WD-40 and my personal favorite - Kroil.

It was only later that I learned that mold can be long dead, but the smell will remain. And by then, I was stuck with a jacket that smelled like WD-40. That took a while to go away and I could not keep it in the house because it smelled like a repair shop rag. I let the jacket sit in the sun for a long time, then washed it in Dawn to get the petroleum solvents out, then put it in the sun again. Finally, I conditioned it heavily. That was over three years ago. The jacket is still with me, although I have put on a few pounds since then. It no longer smells like WD-40 (or Kroil) and still has a very faint mold odor. But it did not make the jacket instantly fall apart, although I have no idea what it did on the molecular level. But the jacket is 80 years old, so I cannot complain.

OK,no WD-40 then..got it!