The problem with grease as I see it is the knife would have to be disassembled to insure the grease is spread on to all the pertinent parts for full coverage. Oil on the other hand can be dripped into the openings, and as we know will mange to spread itself all over the internal parts without the need to disassemble it.
These are just my thoughts on this subject, and I may be totally wrong here.
It is possible to get to the springs without full detail stripping on some of their folders. Removing all screws except the pivot sometimes allows the handles to rotate enough to get inside the area where the omega spring resides. A blunt syringe can be useful for application this way. The problems I find with many liquid products are generally the reasons I use a grease instead for the omega springs. A liquid may not provide optimal reduction in friction (and the primary goal is reducing friction wear), it can migrate (over time it can move off the surface it is intended to be on and that can be messy and ineffective in providing the needed lubrication), it may not do as well with constant changes in temp, humidity, and exposure to water, and I find it rarely gives long-term lubrication of a good grease. The right grease product will often function fine for years after a single application, and thus far I have not used a liquid that gives anywhere near that kind of a maintenance interval. So I am personally biased towards the right grease, especially fluoropolymer grease similar to what Chris Reeve uses on the Sebenza.
Some people seem to say the springs NEED to be oiled or greased to make them last longer. The thinking is that by reducing friction or wear, the metal wears less and lasts longer. Could there be a flip side? Both oil and grease can capture dirt and debris that enter the spring chamber. I kind of think about that area lubed up as being filled with mild wet stone slurry after some time of carry. I used to oil my pivots all the time, obsessively so. For an experiment, I just stopped. Years later I haven't seen the need. I only add one drop after soapy water washing done yearly. I'm not saying to never use oil. It's just for the omega spring issue, I'm not sure lubrication is the answer. I vote on burr on handle scale or metal liner. A groove (microscopic) forms and a stress crack grows from there over time. Option B is they have corrosive body juices, not saying anyone is dirty. Some people are hard on certain watches and jewelry. I'm probably going to try some form of music wire before sending it in.
I use fluoropolymer grease for this reason. It tends to foul up less than most liquids, and is very good at resisting being removed water or migrating over time. I use it on firearms for the same reason...and it greatly reduces fouling compared to other greases such as RIG. The chamber that houses the omega springs are somewhat limited from the rest of the knife on many BMs as the liner is on one side, and the cutout inside the handle for the omega springs on the other. Provided I do not need to strip the knife for some other reason or submerse the entire knife in a solent for a prolonged period, a single application of the fluoropolymer grease I use on the omega springs lasts literally for years. When applied to the pivot, it continues to reduce friction and operate at a consistent smoothness for months at a time, even with frequent daily usage. Even when sharpening with the EP, which makes a ton of muck that gets everywhere inside the knife, the grease is unaffected as it does not mix nor does it wash away or move. Overall, once I apply this stuff to the points of friction in an AXIS folder, that knife generally becomes as smooth as any folding knife can possibly be.
As many of the handles that Benchmade use are made of metal, as is the liner, as are the omega springs themselves, the fact is that omega springs are making friction with other hard surfaces, and this repetitive contact over an extended time results in wear. While it does not eliminate it, good lubricants reduce wear by quite a bit. I strongly feel that this helps prolong the life of the omega springs in many cases. While friction is certainly not the only cause of failure of the AXIS omega springs, it is something that happens to metal and unlike most other causes, it is something we can take action to reduce.
I can't say if it is the right product for other people, but I use it extensively on knives, firearms, vaults, and on a variety of other applications where friction that causes wear is a functional concern, and I find it tends to usually make a big difference in terms of overall performance and longevity.
So to me, I look at lubricants in the same way I do with knife steels: just like matching a steel's performance properties to the usage that particular knife will see, I find matching the lubricant to the application generally tends to yield the best outcomes.
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