I emailed Smith & Allen about it last year, they didn’t even bother to reply!

I can now see their point of view, after all the interest even on this informed forum hasn’t been exactly spectacular, so the general population of owners out there would probably be too scared or reluctant, and a bulk purchase could take a very long time to sell.  “If it ain’t broke, don’t fix it” -where’s the fun in that?

Gremlin, I for one would deffo use the 40 grade oil if one could be made.
From all I've heard a 30 grade can quickly deterioate to 20 which is concerning.
You made a very valid topic by starting this post.