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Heres another comment a friend of mine who is in the industry sent me that is great info:
Before jumping in, I want to note that, even though I own a gun lubricants R&D and manufacturing firm, my rule is that I will always share the truthful science of the pros and cons of any lube in guns. If for no other reason than people may not have access to our lubes in any given situation, and this info is universal, and quite literally life-saving.
None of it is super complicated, but most of the concepts are just absent from our shooting culture still. I'm working to solve that.
Now, your post:
Your data is what I call the "Walmart Gun Lube Test" - what can I use in Walmart to keep my guns running the best?
And this is the critical rule for all of us here to remember, whether talking about wally world lube, our pet lubes, or the lubes my company engineered: the question is not, "Will it lube?" The question is, "How long will it work in my guns, how well, and under what conditions?"
Your data starts getting at that, it's great to see.
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**Bottom line for me on walmart lubes**
If I didn't have access to my lubes, I'd run a 20w50 V-Twin oil in normal temps, and either ATF or 0w20 in the winter. No gun oils at Walmart will exceed the reliability of these oils in guns.
Here's why:
Cold weather:
The key concept to understand here is Pour Points. More specifically, you will get killed if you rely on Pour Points as a "low temp limit". It is also the single biggest point of snake oil claims in the gun lube world.
Sam, as you noted, Pour Points are essentially the low-temp number where an oil will simply not move if you turn it upside down.
The problem is, there is a VERY big difference between "reliable in a gun", and pour point.
It's complicated even more by the fact that oils don't hit their pour points at a linear rate. You can have two oils with a -50F pour point, but one will be dead in a gun at 0F, and another will stay reliable down to -20F. We've seen differences between "reliable" and pour point/low temp claims as wide as 80 degrees. As in, the gun was dead at temps 80 degrees warmer than the gun oil claimed it could go. (We have over 85 lubes I've ever heard of someone using on a gun at my shop, and we've run low and high temp testing on all of them).
All oils have a low temp threshold, where they go from reducing friction, to actually acting like an adhesive. This comes from two factors: adhesion, and cohesion. Adhesion is the oil molecules sticking to the metal, and cohesion is the molecules sticking to each other.
Short chain oils flow better in cold because there's simply less material for other molecules to get intertwined with. It's similar to why long hair will get knotted when short hair won't.
In engineering gun lubes though, a key challenge is balancing between low-temp reliability and high-temp endurance. Short-chain oils typically have much lower flash points, and will often oxidize and/or burn off at temps much lower than long-chain molecules. The flash-point of milspec CLP is 201F - less than half of common motor oil, and it's precisely why it burns off so easily in DI ARs, which have gas hitting the gas key at 1000-1500F. Flash Point is a much better approximator of reliability than pour points, but it's still only one aspect of what happens in high temp, and is still only an approximation. With high-temp endurance, molecule length (and structure) matters like the difference between kindling and firewood - it's a lot easier to get kindling burning. Short chain is kindling, long chain would be like very long tree branches, and ring-shaped molecules are like rounds of firewood. We use a blend of all three, depending on the application.
Of all the lubes on the market that we've tested at our shop, only about 8 are reliable in a gun at -35F. Almost all of them are thin. Except ATF.
CLP is dead in a gun at about -30F (Ask Fort Wainwright). 0w20 craps out about -25F. ATF goes to about -30/-35F. One notorious gun oil claims it goes down to -110F, yet it's as thick as honey at -20F. I have several "gun greases" companies have marketed to gun owners that look like repackaged #2 industrial greases, where they claim to go down to -50F or -60F, but are dead in a gun at 10F, and almost rock solid at -20F.
So, in low temps, 0w20 down to about -10F, ATF if you need to go down to about -35F.
And the great thing about ATF, is that it's far thicker than gun oils in normal temps, and is an actual CLP, far better than Milspec CLP, because of the way its polar molecules work. Overall, ATF is a very good gun oil, but not quite as good in wet weather as you'd like.
BTW, I should say at some point that we don't even manufacture a "gun oil" - we've engineered 7 lightweight greases. They keep guns running about 10x longer (ARs get 2000-5000rds on one application), and they stay wet, stay put, and stay reliable for over 2 years in place, shooting or not.
Outside of the gun world, you will virtually never find an unsealed, sliding machine that uses oil - these are always indicators for using a grease, especially when there are no lubricant support systems (gaskets, pumps, filters, reservoirs, etc). Oils are designed to flow, and to pick up and transport friction contaminant way from your friction surfaces - in guns, that's why they flow out, thin out, and dry out, and it's also why sand will get migrated right into friction surfaces with oils. Grease acts like a sealant to keep crap out of your friction surfaces, and it stays put. Sand may get stuck to the outside, but the grease will keep it there - away from where it causes problems. Properly weighted, it will also push sand or other fouling to the front and back of travel if it does get blown in somehow, leaving it stuck, safely, at the front or back, out of the way. Our greases are properly weighted, and won't get gummy, even in nasty sandy environments.
Our heaviest grease is about the consistency of a creamy mayonnaise, the lightest almost feels like a whipped cream, but with no air. That's our Winter Balm.
It will keep ARs running down to about -65F, with stone cold reliability.
20w50: 1) Additives, 2) stays put better unsealed sliding machines (ie, guns) better than thinner oils, and 3) ability to achieve hydrodynamic lubrication.
ADDITIVES: are things like corrosion inhibitors, boundary lubricants (slick solids, like moly, teflon, or graphite) and in this case, something damn special: ZDDP. It flashes to a microscopic, ultra hard, slick phosphate glass, that is both an anti-wear and anti-friction coating. It's as close to magic as you'll find in tribology (the science of friction & lubrication). It's also 70yo tech - it used to be in all motor oil, but it clogs catalytic converters. But, you can find it in bike oil. We also use it.
THICKNESS: will help it stay put. The 20 number is "acts like a 20 weight when cold" the 50 is "Acts like a 50 weight when hot". Oils thin out when they get hot. When cold, the shorter the molecule chain lengths the "thinner" the oil, the longer the molecules the thicker. You mentioned viscosity index - the PAO oils used in motor oil have relatively low VIs, meaning they thin out quickly when hot (a couple of the oils my company uses have VIs over 200). Chemists use additives that are tightly wound long-chain polymers when cold, that unwind when hot, which thickens the oil. Engineers try to keep motor oil acting with the same viscosity no matter what the temp, so these viscosity modifiers are carefully engineered. 20w is pretty thick at ambient temps, so it won't run out of your guns as easily, but when they get hot, these additives thicken up the oil to, again, help keep it from running out of your gun.
HYDRODYNAMIC LUBRICATION: is the big one - this is what you want. If you achieve it, it's like hydroplaning your car on a wet road - and the parts literally do not come into contact with each other. It's why your car motor can get a billion rotations in its lifetime. When you don't achieve it, the parts rub against each other, and the tips of asperities (sometimes erroneously called "pores") break off. And that's all wear is, broken-off asperities.
With hydro, the lighter the fluid, the faster the parts have to go to float - it's similar to why slowing down prevents hydroplaning on the road, or why a water skier needs a minimum velocity to get on top of the water. This lighter fluid needing greater speed for the moving parts to float is called the Stribeck Curve, and it's a fundamental pillar of tribology.
It's also why your car motor will have less wear after a 100,000 rotations than a new gun will after a box of ammo, when using gun oil. Car pistons move about 7x the speed of slides and bolts - car oil is simply too light to achieve much hydro in guns. But they also tend to be a lot thicker than gun oils, which is a large part of why they perform so much better.
So, of all the motor oils, 20w50 is what will give you the best hydrodynamic lubrication in guns - meaning the least wear and and least amount of friction.
However...
You do *not* want to go with the much thicker gear oils. Mostly because of sulfur based extreme pressure additives - they can cause severe corrosion in some circumstances in copper, brass, and other metals, and can lead to copper disulfide, which is an abrasive. It will also freeze your gun dead/unreliable at much warmer temps than the 20w50. CAVEAT: USE IT if it's all you have in an emergency in normal temps - it will be vastly more reliable than running your gun dry.
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