[picinkoff]

Lapkritis, you are absolutely correct.
We should all consider the use of new or different products such as krytox.
It may be well worth investigating the use of this product in our air-cooled engines!

But... At the same time, I also understand what Henry is saying.
The study you present from the use of Dow 55 on various materials is, no doubt important.
But, the effective loss of tensile strength, does not necessarily apply or affect our intended use of these products.

Also, there is something else that perhaps was not mentioned, or forgotten, in these recent posts.
As shown in your last picture of the red o-ring, it appears that there is little, if any, chamfer in the engine block. This, I believe is important. Assuming the same size o-ring in a block with and without chamfer, the effects will be quite different. You will likely have more force placed on the o-rings by the treads. A similar effect would occur on the other end, effectively over compressing the o-rings between the block and washers, likely resulting in premature failure as well.

Improper setup can also be the root-cause for a lot of these issues.

The purpose of DOW 55 is to swell the o-ring into a properly chamfered section.
I believe, if you don't have that chamfer setup, then you will have premature failure regardless of o-ring types and lubricants used.

Paul Icinkoff