Q: Upgraded ram to 8gb but only show 4gb free?

Perfectly normal behaviour. The Operating System will utilize as much RAM as it requires to improve performance.

Again, your computer is handling the extra RAM you have added exactly as it is designed to do. Any App that proposes to "free memory" is a waste of time and money. Unused RAM is wasted RAM.

http://www.switchingtomac.com/tutorials/osx/understanding-memory-pressure-in-os- x-mavericks/

Agreed, for the most part: RAM is the fastest medium to keep and process data, so the more is used, the faster your machine will work. Caching/writing to disk (even an SSD), on the other hand...

Now, about those "memory cleaning" apps: there are the good ones, that actually clear inactive memory based on real alloc/malloc instructions left by running apps, and those, not so good, that will clean indiscriminately, shaving at the top, so to speak.

One good app that will work, though in your case it's pretty useless, given the total amount of RAM on your machine, is Purge; you can also invoke the "purge" command in Terminal every once in a while if you want, but it's not going to change the face of the Earth...

You may find this article informative:

http://support.apple.com/kb/HT5890

Ciao.