Grease on lens mount

[f1charlie]

When I took the lens off my D90 last night I noticed a smear of what appeared to be grease or lubricant at between about 7 and 8 o'clock position on the camera lens mount. I haven't had the lens off much so don't know if it has always been there. Is this normal?

 

[jaffamuffin]

Some people put a bit of grease on the threads to catch any tiny bits of metal that may appear durign the natural action of threading something, also it's a mechanical thread. A bit of grease will be good for it. (a small amount)

 

[f1charlie]

So do Nikon do this for new lenses/cameras? This is the 18-105 kit lens. I had noticed that it did attach/detach very smoothly!