Short answer: if the knife touches food, use food grade mineral oil. If it never touches food, a light machine oil works and lasts longer. Do not use cooking oils from your kitchen cupboard, and do not use WD-40 as a protective coating.
Food grade mineral oil
This is the default answer for kitchen knives, and for any carbon steel blade that might touch food. It is sold as food grade mineral oil, butcher block oil, or in a pharmacy as light mineral oil. All the same thing.
It is odourless, tasteless, does not go rancid, and it is safe on wooden handles and cutting boards as well as steel. A bottle costs a few dollars and lasts years.
Do not use kitchen cooking oils
Olive, vegetable, canola and sunflower oil all go rancid. They oxidise, turn sticky, smell sour and can leave a gummy film that traps moisture against the steel. That is worse than no oil at all.
The exception people ask about is camellia oil, which is the traditional Japanese blade oil. It genuinely works and does not go rancid quickly, but it costs more than mineral oil and does the same job.
Non food knives
For a folder, an EDC blade or a hunting knife that will not touch food, a light machine oil, a dedicated knife oil, or a corrosion inhibiting oil lasts longer than mineral oil and protects better against humidity.
For long term storage a rust preventative such as a light gun oil is the strongest option, but wipe it off before the knife goes near anything you will eat.
Where WD-40 fits, and where it does not
WD-40 is a water displacer. It is genuinely useful for flushing a gritty pivot or driving water out of a knife that got soaked. It is not a protective coating: it evaporates and leaves a thin residue that attracts dust. Use it to clean, then oil the knife properly afterwards.
How much, and how often
Far less than people think. A few drops on a cloth, wiped over the blade until it looks barely damp. If you can see wet oil sitting on the steel, wipe more off.
| Kitchen knife | Wipe after washing. Oil monthly. |
| Carry folder | Blade monthly, one drop on the pivot. |
| Hunting knife | After every use, then before it goes away. |
| Long term storage | Oil well, wrap in paper not plastic, and never leave it in a leather sheath. |
The sheath problem
Leather is tanned with acidic compounds and it holds moisture. A carbon blade left in a leather sheath for a season will come out spotted no matter how well you oiled it. Store the knife out of the sheath, every time.
Questions people ask
Do stainless knives need oil?
Stainless resists rust, it is not immune. 440C and D2 both spot in humidity or salt air. Oil them less often, not never.
Does oil affect the Damascus pattern?
No. The pattern is forged through the steel and the etch sits in the surface. Oil protects it. What fades an etch is abrasive polishing, not oil.
What about the handle?
Wood, bone, stag and horn all benefit from the same mineral oil once or twice a year. Micarta and G10 need nothing.
My blade has already spotted
See how to remove rust from a knife, then start the oiling routine above.
More from the workshop
How to Tell Real Damascus from a Printed Pattern
Four checks that separate forge-welded steel from a surface-etched imitation.
Knife Blade Shapes Explained
What each blade profile is actually built to do, and which one you want.
How to Store Knives Properly
Contact and moisture are what ruin stored knives. Both are easy to avoid.