If you are running Linux and haven’t set your locale yet, FuelPHP may be running with the default en_US and silently logging a warning if your system doesn’t support the locale. Often, Linux systems have the locale “en_US.utf8” instead, but you can determine what is available with a “locale -a”.
The logs located in fuel/app/(year)/(month)/(date) will tell you if there are any warnings. You can run a “php oil help” from the console to generate an entry in the log file if there is a problem with the set locale.
Harro Verton, thanks for the tip on determining existing locales and on using en_US.utf8.