What is the default compression level for local synchronisation?

[Charles]

Searching the 'net showed that rsync asks zlib to use default
compression which is equivalent to --compress-level=6
(http://samba.2283325.n4.nabble.com/what-is-the-default-value-for-compress-level-tp2538905.html)
but that would not be a good choice for local synchronisation.

Should we use --compress-level=0 for local synchronisation?  We are
using rsync 3.0.9 and 3.1.1.