It is generally not a good idea to delete your server's log files as this could cause problems with the functionality of your server when a process tries to write something to a log file and is unable to because the file is missing. Removing the /var/log folder would most definitely cause major issues with your server. However, your server should be archiving old log files, and those should be safe to delete if you do not need them. Old log files will have file names ending in .1.gz, .2.gz, .3.gz, etc. You may want to back up these files to a remote location before deleting them from your server just in case you find that you need them later.