jka-compr-load-suffixes

jka-compr-load-suffixes is a variable defined in `jka-cmpr-hook.el'.
Its value is

(".gz")

Documentation:
List of compression related suffixes to try when loading files.
Enabling Auto Compression mode appends this list to `load-file-rep-suffixes',
which see. Disabling Auto Compression mode removes all suffixes
from `load-file-rep-suffixes' that enabling added.

If you set this outside Custom while Auto Compression mode is
already enabled (as it is by default), you have to call
`jka-compr-update' after setting it to properly update other
variables. Setting this through Custom does that automatically.

You can customize this variable.