Dry graphite has worked well for years, and is the choice of locksmiths nationwide. I would usegraphite, no need to reinvent the wheel for something that needs to lubricated every couple years.

Dry graphite is the only thing that should be used in a padlock, or any kind of lock for that matter. Especially a padlock that is used outside. While lubricating or penetrating oil might seem to work for a while, it will attract dust and gum up inside the padlock. This is the reason why everybody seems to recommend dry graphite. Because it works.

Thanks, I see. [sigh] though I decided for now to postpone decisions.

Please don't get upset, but firstly, why would a widely popular company such as WD40 want to risk their reputation by marketing Item #3 above, if its so risky to use compared to dry graphite?

Secondly, here's what AI states about Houdini vs dry graphite

(also there have been mixed votes on Quora on this topic)

Houdini is widely considered the preferred choice among professional locksmiths. While dry graphite has long been used in lock maintenance, it is often viewed by modern professionals as a messy option that can gum up or turn into a thick paste if mixed with residual wet lubricants. [1, 2, 3, 4, 5, 6, 7, 8]

Why Locksmiths Choose Houdini

• No Residue: It contains absolutely no oil, grease, Teflon, silicone, or graphite, leaving no sticky buildup to attract dirt.
• 4-Way Action: It penetrates, cleans, lubricates, and protects locks against rust and corrosion.
• Safe Application: It is safe for electronic locks and delicate components. [1, 2, 3]

Why Dry Graphite Has Fallen Out of Favor

• The Mess Factor: It frequently leaves a messy, black, metallic powder that can stain keys, pockets, and doors.
• Humidity Issues: In humid or wet environments, moisture in the air can cause the graphite to clump up or harden, actively jamming the lock instead of freeing it. [1, 2, 3, 4]

Do what you want then, why keep asking when AI has all your answers...................

Not just AI. On Quora too, i saw it being debated. Unless - is it possible the debaters were bots too?