I think it is a combination of soft alloy aluminum plus poor machining or threads that are too thin. I suspect the grey is bits of aluminum that flake off when you twist and mix with whatever lube you use. Not a problem with annodized, but also not a problem on several thick thread bare aluminum ones I have. Seems to be a symptom of cheapo flashlights.
Next up? I'm going to test shredder oil. I used to work for Fellowes and I forgot I have a bottle of fine machine oil used to lubricate cutter blades.
I am thinking that the Quark threads were flaking from the very beginning (bone-dry state) and i didnt notice it because the aluminum powder was dry and mixed with the o-ring abrasions, dry too. i had been using a toothbrush to scrub the threads (and the brush got grey/black instantly). When the grey powder gets mixed with *any* substance (grease, oil, ..), then the abrasion becomes more apparent and visible: grey cr*p!, which should be removed the sooner the better before it does self-damage and accelerate the abrasion.
Quarks are not known for wear-resistant top quality machined threads (Sunawayman). If the Quark threads were anodized, there would be no abrasion -- no matter how poor and cheap the machining is.
If i ever buy another torch in future .. i will pay attention to this detail: all threads *must* be anodized!!
their suggestion is listed on their website: Deoxit
no way i am gonna use this. i had already trusted in buying the Quark "quality", that's enough.
from what i can tell, the Nano-Oil.com stuff should be the best .. but before i spend another 16$ on lube, i better buy a new anodized flashlight for this kind of money ;) Another Romisen or so. Apart from the choice of lubing product, the Quark's threads and machining is indeed "not on a quality level with Sunawayman or Klarus" .. to phrase it extra mildly.
If the threads themselves were thicker and top-quality stuff, then i would look into buying the Nano-oil; it would be worth the efforts and investment.
Since the Quark threads are the way they are (you named it, i didnt!!), there is definitely no point in buying even better lube than the Superlube. I will continue to observe and report back. So far my observation:
Superlube oil kills the friction (mainly caused in the fat Quark o-rings) but the Quark bare aluminum still gets eaten up with the twisting action and you dont feel it because Superlube kills all friction. This makes one wish for a Titanium Quark (too expensive and heavy!) or anodized threads!!
I just bought a bottle of this same Radio Shack Precision Lube today, and it's great. I did a little research and lo and behold this is "Super Lube" oil. It's even got a "Synco" pocket clip on it. I assume Synco (makers of super lube) sells it to Radio Shack and then Radio Shack slaps their name on it. They call it "Needle Tip Precision Lubricator". It cost me around $3.99 for a 7ml bottle.
my superlube oil works extremely well on (any kind of) o-rings and anodized threads.
it kills friction in bare aluminum threads (e.g. Quark threads) but doesnt really reduce abrasion (build up of "grey crap" is still there)
on titanium threads it doesnt do anything noticeable. i even get build up of the grey cr*p which i dont seem to get with other/no lubes. thats why i dont recommend superlube oil on titanium threads. maybe superlube grease works better on Ti threads.
I thought I remembered hearing it was on a CPF thread once. Works pretty good. I remember hearing this being the best low cost option since it was compatible with most of the metals and rubbers in lights.
Unfortunately not carried at all retail locations. They also carry a Anti-Corrosive Lubricant Spray which I have found useful. Like WD-40, but leaves a slight oil film. It has help me unstick a few pills/switches that seized up.
Hmmmm, not sure I agree with that assessment. I clean threads with mag wheel/aluminum cleaner before I apply grease or lube. Doesn't matter, threads still turn grey regardless.
mildly.
Missed that; You need to use more smilies next time. 
I'm usually better at spotting ironicals.
