as I wanted to increase the space surrounding the = sign in my equations, I changed the thickmuskip length in the preamble
\setlength{\thickmuskip}{14mu}
It works fine, and I like the result in display-style equations. The problem is that it also affects equations written in text-style (ie those with $$) and there it does not look good. How can I get a different spacing around = in display and text mode?
Thanks
\everydisplay{\medmuskip=10mu\relax}as suggested in the answer causes an error for me, in the amsmath package:\begin{split} won't work here. The document builds perfectly without the\everydisplay– Bruce Jun 27 '14 at 13:00\everydisplay=\expandafter{\the\everydisplay\thickmuskip=14mu\relax}. See answer by Matthew Leingang – Bruce Jun 27 '14 at 13:11