Electricity 
Some lights have bare threads through which the current must flow.
Dielectric Grease all the way! It waterproofs and insulates electrical connections. It’s safe for the O-rings too.
On CPF, I had read that Mobil 1 synthetic red grease in the grease gun tube worked well. I bought some for my lights and for repacking bicycle bearings and it’s worked very well. It has a strange smell but once the light is screwed together, it wasn’t noticeable.
Same here. It’s kind of pricey but I’ve been using the same tube since about 2007 on numerous lights. A little bit goes a long way. Great stuff.
2012 here and I still have a lot left.
I may even try and repack my SWM V11R with it!
Chris
I think I got mine around the same time, Can’t even hardly tell I have used any. I got a Lifetime Supply I guess.
It probably work in the V11R, might make it less resistive to turn.
Sil-glyde too. Always used it on my caliper slider pins and now on my flashlights.
I’m amazed no one’s linked CPF’s thread on the matter. It’s very comprehensive.
I use Super Lube on everything.
Thanks, might get a tube never tried it before.
Nitecore Silicon Lube.
Liteflux Silicone Lube. Enough for the next years… 
Pricey:
Molykote 55
Molykote 111
Cheap:
Olive-oil
The “preferred” Super Lube 21030 Synthetic Grease is also sold at most Harbor Freight stores, so those fortunate (or unfortunate?) enough to live near one can use one of their ubiquitous 20% off coupons for an even better deal (which CAN be combined with a free flashlight coupon = flashaholic Nirvana).
So many choices, but there are basically only 2 types:
- hydrocarbon based (petroleum)
- silicone based
HYDROCARBON
Vaseline/petroleum jelly
Mineral oil
Food oils
Waxes like paraffin and beeswax
Super Lube
Nyogel
Nano Oil
SILICONE
The greases sold by most flashlight brands
Plumbing and scuba greases, I hear
YES, the beloved Nyogel and Nano Oil are petroleum-based. Don’t take my word for it, here’s the MSDS of Nano Oil: http://www.nano-oil.com/Nano-Oil_MSDS_NLNA-5-10-85_20070415\_.pdf
- Highly Solvent Refined Paraffinic Petroleum Oil
- Extremely Hydrotreated Heavy Naphthenic Mineral Oil
- Detergent, Inhibitor & Dispersant System Highly refined Mineral base Stock distillates
So those o-rings that work with Nano Oil? I think they’ll be fine with vaseline.
But the way I see it, hydrocarbon greases are the safest bet. As flydiver said, both petroleum and silicone o-rings will be resistant to hydrocarbon/petroleum greases.
BUT silicone greases will attack silicone o-rings. We’re just lucky no flashlight manufacturer uses silicone o-rings.
It says dielectric. Shouldn't make any difference, but if a flashlight had a mechanical lockout and the anodized threads were just a little worn, wouldn't the dielectric grease make it even easier to make electrical contact and disable the mechanical lockout?
Nothing like this:
Use it for anything you can imagine but the best use is for guns and flashlight threads. It stays on threads almost forever in any type of environment.
My recommendation as all in one lube. I use it for years and I used some expensive stuff before that can not match it so I know how it works and I can recommend that to everybody.
Nice that I learn as I read this thread. But there’s one lube I’ve been using and it’s lithium grease.
Was told that it is bad for flashlight but can’t remember why. Petroleum based like vaseline maybe? I’m not sure
Maybe I should spend some time googling before I comment.
So far I like it because it is white. If it is grey or black I know its time to clean. (hopefully it’s not eating my light or orings as I used it for 3 years and still looking good)