finish line extreme fluoro grease is the recommended standard for couplers which is out of stock locally(shakey isles)and also in many areas around the globe. What would be an available alternative, I see finishline have a synthetic PTFE grease(readily available locally) and assume this would do the trick? Any thoughts appreciated

Last I knew, direct from the coupler manufacturer, no recommended alternatives exist. The 'approved' recommendation remains as -
Dupont Teflon Bearing Gel or the Extreme Fluro Grease.

The two are one and the same, with regard to S&S coupler application.

From the S&S site:

"The DuPont Teflon® branded grease, that we previously sold, was discontinued by DuPont and our inventory is depleted. We now carry Finish Line Extreme Fluoro which is made specifically for us by Finish Line from the same 100% pure DuPont fluorinated ingredients used to make DuPont Teflon® Bearing Grease. In our tests, Extreme Fluoro performs as well as DuPont Teflon® Bearing Grease and for our purpose, we consider it to be equivalent to DuPont Teflon® Bearing Grease. Teflon ® is a registered trademark of E. I. du Pont de Nemours and Company"


That said, shortages have happened before, more than once. To prevent that from happening again, an investment was made in inventory! Sale prices can even be found but costly shipments, over the pond, are likely not all that feasible.

https://www.precisiontandems.com/cat...htm#lubricants

What’s the problem with using just regular bike grease?

Good question that's what I have been doing since I can't get the recommended stuff, I suspect regular maintenance is more important but would happily use the fluro stuff if I could get my hands on some.

My experience with other kinds of grease on S&S couplers is that it's trickier to tighten the couplers completely (right to the last thread). Teflon grease makes that easier. S&S's special wrench isn't that long so one can't just torque it like a normal bolt assembly. The coupler "nut" can and has backed off on me when I don't really tighten it down.

I bought, what I figured, was lifetime supply of the right Teflon grease off Nashbar when they discontinued carrying it 20+ years ago, Still have some.

I have switched to z-connector (designed by Santana) for my new (single) Ti travel bike. Using a standard hex key is so much easier than always carrying around the S&S wrench. According to Paragon when I called, I could use some copper anti-seize if I am not going to take the frame apart for a while or some purple Loctite if I am worried about the bolt backing out.

More than most ever wish to know found here. Steve states that some lubricants are actually worse than none at all. I would sum it up as 'galling'.
https://sandsmachine.com/grease_t.htm

I contacted finish line here is their responsiveWe’ve discontinued our Finish Line Extreme Fluoro. The direct replacement you’re looking for is InfinX MRO KF205. We re-package Extreme Fluoro for Halo Carbon, which has the same formulation and is readily available on Amazon.

https://a.co/d/3R4nk8z

Nice ridiculous price. Thankfully there are "official S&S approved labels" for a fraction of that cost.

After seeing this post I began a search & found that TICycles.com out of Portland, Or., has tubes of Finish Line Flouro Extreme lubricant for $18 so I picked up a couple.

Has anyone actually experienced issues with using regular grease? I have a tandem and a triple tandem with couplers that I use Phil waterproof grease on and have never had an issue. Have I just been lucky?

S&S has done extensive testing, including Phil waterproof, see their list. There is reason to believe that they want the best product for their customers. The couplers experience much transverse force. I would not want to depend on luck when touring in the middle of nowhere.

post #5 describes dissatisfaction with using regular grease on couplers. Although just one anecdote, I find it more compelling than the extensive S&S report where no evidence is ever presented showing 1/4x20 nuts deformed under 4000 pounds of lateral force as a valid simulation for bicycle couplers. I suppose that it’s a quick, easy and inexpensive way to compare galling failure limits between stainless steel threads across scores of lubricants. But not necessarily translatable to a much different application.

Couplers tend to gall, said the voice of experience. Having one freeze up and the cost to repair makes the small investment the right choice.

I agree that it’s not a completely accurate representation of the loading the coupler would see but I definitely appreciate that they developed a test method and have quantifiable results. I put more faith in a well designed test than in one anecdotal result. But since the test is not an apples to apples comparison, I would definitely like to know if others have had issues. Post #5 mentioned having the coupler loosen but has anyone had issues of it actually galling? That would show up as damage to the thread surfaces themselves or possibly on the coupler teeth(?).

I have worked on a tandem that had two galled couplers (a couple of others with 'sticky' ones) with reported lithium something or the other used. The two described finally freed up after a doubtful period of wrestling time and resumed mostly normal function after a thorough cleaning and lubrication with the Krytox bearing grease followed by working it back and forth many times, recleaning and re-lubing. The potential for seizure or galling is greatly exacerbated by the fact that a large threaded surface area is involved due to the many threads engaged, and the largish tube diameters used on bicycles, particularly tandems. To me it is not worth the risk, given the cost of repair. Steve at S&S has obviously discovered a problem, found something that works, that protects his product, and his reputation. And it is doubtful that there is any personal financial skin in the game with Dupont. Combined with 30 years experience of seeing the stuff work when following Steve's recommendation, it is easy to also hang my hat on the same hook.