How to clean /var/cache?

When I woke up this morning, I found my root had filled overnight

du -hx --max-depth=1 /

132M    /boot  
4.0K    /media  
16K /lost+found  
16M /root  
702M    /lib  
4.0K    /OLDHOME  
8.2G    /usr  
73M /etc  
4.0K    /srv  
11M /sbin  
4.0K    /selinux  
8.0K    /.config  
4.0K    /cdrom  
4.6G    /var  
181M    /opt  
4.0K    /mnt  
9.3M    /bin  
4.0K    /lib64  
14G /  

The space is used by /var/cache/polipo (2.7G). How can I clean this up safely?
I tried restarts=>didn't work
Used bleachbit=>the space is not detected in the cleanup preview

PS: I did rm -rf youtube inside /var/cache/polipo and it freed up 2G space. Dunno if it was safe though

Method 1:

sudo apt-get autoclean
sudo apt-get autoremove

Method 2:

Launch your bleachbit as root user : no space in disk; sudo apt-get clean not working

Polipo, a web caching program may store a lot of data in an on-disk cache.

One way to clear this up is to issue the command sudo polipo -x - this will cause polipo to clear the local disk cache.

The most powerful of all commands to clean the cache for command line users is of course

sudo apt clean

Which will also delete all the cached files.

Try cleaning ubuntu unnecesarry files using bleachbit. It is a tool that will help you clean your cache, temp files, cookies and it has other features also...

To install it:

sudo apt-get install bleachbit