[mauvehaus]

Thanks for the link! MSR uses leather pump cup seals in their liquid fuel stoves, and it's nice to get some background on why this is the best choice from an engineering perspective.

I'd intuited some of the points in the article, but it's good to know that somebody has approached the subject rigorously, and taken the time to explain why leather is superior in this application.

[Xylakant]

In a fuel pump, the washer also has contact with substances that are aggressive to rubber: the stove fuel itself. I doubt a rubber o-ring would survive long in that environment.

[dwater]

There are fuel resistant rubbers available, most commonly Viton/FKM. They are commonly used in automotive applications.

https://en.wikipedia.org/wiki/FKM

[mauvehaus]

The pump cup, in theory, never touches fuel. And goodness knows MSR isn't shy about using O-rings. There are nearly half a dozen in a Dragonfly between the pump and the stove. They're using a material that holds up to fuel contact for those.