ATF has a lot of polymer content known as friction modifiers to keep it more stable under shear thus less susceptibleto viscosity reduction while in service, much like multiweight motor oils. There are specific high $$$ patents and proprietary / licenseor rights to many of the formulas including ATF+4, Dexron VI, and Mercon LV to name some of the older such fluids. Automotive greases are akin to soaps with significant solids added for the rolling friction environments they're formulated for.
For corrosion resistance the most important part of the picture is excluding anything that can lead to that reaction. So theoretically a uniform oil layer as thin as one molecule wide that doesn't decompose into anything acidic would be sufficient. The reality is all oils break down over time in environments with oxygen present and even slight traces of water, moisture, allows acidic substances to ionize.
The breakthrough in synthetic lubricants, including firearms, came during WWII with the Axis forces experiencing difficulties during the winters by their forces in what was then the USSR with for their time anyway finely crafted machinery. I haven't personally read of similar problems experienced by the forces of the USSR WRT small arms, and their forces were noted for building small fires under the engine compartments of their diesel powered vehicles (I haven't seen details but mymental picture has a fire to one side with coals / embers being periodically shoveled under the engine compartments rather than a blazing fire directly underneath but who really knows). With the ever evolving automotive engine oil requirements today many oils ate required to have some synthetic base oil content to meet manufacturers' specifications with European such as VW, BMW, Porsche, etc. being generally recognized as having some of the most difficult to formulate for. But I haven't yet seen bottles of plain synthetic base oil on the shelves at WM. Mobil 1 stopped using their definition of purely synthetic base oil (before their conflict with Castrol on that definition) around 15 years ago when several hurricanes wreaked their fury on the XOM manufacturing facilities for that material and have been blending Mobil 1 with (extremely high quality) base oil from crude oil since at least outside of Germany. It's all marketing terminology to a molecule manipulator like me as ethylene derived from cracking of petroleum is the building block molecule Mobil formerly contested was the only lubricating base oil worthy of the term "synthetic", and Penzoil's process from natural gas cost an eye-watering $25 billion, five times the cost of a refinery with similar volume product capacity producing an indistinguishable frm a performance perspective product from crude oil with the appropriate equipment and catalyst configuration.
I've never used materials like Froglube uit I've seen mixed user reviews so I just stick with the same old Outers gun oil my dad used from Wyoming to Texas. It never let him down but if I was going hunting in extreme cold temperatures I'd see about testing how my rifle including lubrication stood up to that first if I could. Somehow the USSR firearms funcioned well enough 75+ years ago which may be in part attributed to larger manufacturing tolerances. I haven't looked into what Canadians or Scandinavians use for their hunting rifles but I'd do so if I had a really cold weather hunt coming up.
Again, to each his own & YMMV. Nothing succeeds like success. What works, works (and what doesn't will reveal itself at some set of conditions and time period).
