I have a knife with 154cm steel on it and I always here that you should put oil on it to keep it from rusting but I am just wondering what kind of oil? And how do I apply it and do I just leave it on there?
If the knife is stainless steel, then you don't have to worry about it rusting, unless you leave it sheathed in a wet sheath. Be sure you clean it off before folding it up or re- sheathing it. For carbon steel blades, almost any good household oil will work. 3 in 1, Rem oil, etc.
There are several grades of steel and other types of metals used in knives. Like another user said, if it is something like 420 Stainless Steel (a very common knife steel grade), then you should not have to worry about it rusting. I still apply oil to my stainless steel knives though to keep the action smooth. Non-stainless will require oil to prevent rust if you are planning on using them heavily. There is a such thing as knife oil and you can find it online. A lot of car or sportting lubricants will work though. I use Rem Oil, a popular gun oil that you can find at Wally World for about $3 a can. Disassemble your knife. Use a solvent and a cleaning solution to clean off the old oil, dirt, and gunk. I use Hoppes solvent (a solvent that can be found at Wal-Mart for a few bucks) and either pour it into a small shot-glass and dip a toothbrush in it, dampen a wash-rag with it, or pour some in the cap and dab a cotton swab on it. Using one of these tools, I swab down my knives completely, focusing mainly on moving parts and parts of the knife that experiences high abrasion (the lock of a liner lock knife for example). Then I spray it down with Rem Oil. Reassemble the knife and let it sit overnight. The next day, I'll rub off any excess oil from the grips. Usually though, the knife is ready to rock the moment I reassemble it. So that's cleaning knives in a nutshell: take it apart, clean off the old oil and dirt, re-oil it with gun oil, then put it back together.
It's stainless steel so it doesn't really need to be oiled. Anything will do for oil if you want to wipe it down. Just put a little on a paper towel and give it a once-over.
I don't know that steel, or what kind of knife it is, but unless it is a kitchen knife use the same thing you would use on a gun. Use an oil that dries, like Eezox, or use paste wax, or BreakFree, or Corrosion X.