These are not Formula 1 engines...they probably do not need oil, but these are tools with moving parts and they are not disposable purchases for most of us, so why would you not use some lubricant?
Some people use very exotic lubes. There's no real reason to do so, other than that it makes you feel better about how you're caring for the knife. Anything that doesn't polymerize is fine. I generally use Tri-Flow or CLP except for frame locks, which I lube with CRK grease.
I used to use Tuf-Glide but don't any more. It attracted and held a large amount of grit, dirt and lint in the knife. The "oilier," wet products don't do that anywhere near as much. Tuf-Glide is a superior rust preventative and I continue to use it on non-stainless blades, but not on moving parts.
They do need lubricant, not for lubrication alone but heat dissipation. May be the pats are coted with Nickel Boron, but the tolerance is still to tight. The engine doesn't even move without heating oil and block to operating temperature. If you stall the engine, you virtually trash it. Not intended to be "disposable" purchase, but don't have much choice. They wear down quickly.
Coming back to this a little late. I assume you're talking about the engines, not the knives, right?