"Gun lubes - grease vs oil:
For those who don't yet know me, I own CherryBalmz Weapons Lubricants - we've been engineering gun lubes for about 6 years now. Those who do know me, know I enjoy sharing the universal science of gun lubes in general, and don't just shill for our products.
In another gun group, I was just asked about the broad differences between greases and oils for guns - it's something you all might appreciate, no matter what your current lube is.
Here's the basics:
Greases are classed as sealing lubricants, while oils are classed as flow lubricants.
Unsealed machines get greases, while machines with lubricant support systems, like gaskets, pumps, filters, and reservoirs, generally get oils - because the oils are designed to transport friction contaminant away from friction surfaces.
When you remove those lubricant support systems, the machine is now unsealed, and oils will flow right out of those friction surfaces, with just gravity and motion alone. The machine will get only a tiny fraction of the cycling it would have otherwise had, before you need to jump in and fix things - in effect, serving as the lubricant support system yourself.
Greases act like a sealant - they stay put, and keep friction contaminant away from your friction surfaces. That sealant effect also applies to the grease components themselves - upper layers of the grease trap air and oxidative elements away from the lower layers of the grease, keeping it fresh and reliable for years on a machine. Junk may build up on the exterior of the grease, like a crust even in cars and major machinery exposed to the elements, but the friction surfaces and lower layers of grease are fresh, clean, and protected.
The biggest misconceptions about grease are that it's basically "sticky peanut butter", and that it will clog up in guns. And for the NLGI #2 greases that are virtually all anyone sees, this is largely true - it's just way too thick for optimal reliability in guns. But greases come as light as cooking oil (NLGI #000) and as thick as a block of clay (NLGI #6). Our firearms greases, being optimized for gun energies and gun realities, are all lightweight, the heaviest being about like a creamy mayonnaise, around NLGI #0.
Because of all of these factors, you could have pure unicorn tears as an oil, but it will still flow away, and pick up and suspend friction contaminant, often migrating it right into your friction surfaces. A properly weighted grease will stay put, and seal junk out. The difference in performance for total round count between gun oils and our greases is about 10x. Most ARs need to be re-oiled every 250-350 rounds, depending on the oil (some will do more, usually thicker ones like Lucas or 20w50 motorcycle oil), while our Black Rifle Balm typically gives about 3000-5000 rounds on one application. And it stays wet and reliable for over 3 years on a gun.
If you want to use oils, for a number of reasons, go with thicker oils in spring, summer, and fall, then switch to a lighter oil, like ATF or 0w20 in winter. If you want to use grease, look for the lightest you can find. Besides ours, Geissele's is great, and lubriplate offers an NLGI 00 that's pretty good. I don't want to sound salesy, and won't get into what makes ours different here, but you'll be safe with any of these greases.
Just remember, the question with any gun lube isn't, "Will it lube?", but, "How well will it lube, for how long, and under what circumstances?" The issue is understanding a given lube's limitations - know those, and you'll be safe.
That said, here's a "grease vs oil" application guide you might find in any plant maintenance handbook, or Tribology 101 textbook - take a look and see what column better describes the realties of guns:"