Getting the MacBook Air up to speed
We would like our MacBook Air to be up to par like it was from the day you bought the device. Here are some things that can be done to do just that.
Another way of speeding things up is if the files inside the Macbook Air already secured permissions. To do that, open the Disk Utility and choose the main hard drive from the sidebar, then click on First Aid and Repair Permissions.
However, this solution will not work if the OS is already in El Capitan, because the System Integrity Protection found with this OS prevents modification on permission for files.
Get rid of desktop clutter
It is important to note that each file on the desktop is a window with an image, whether an icon or a file preview. Each window and its contents are stored in RAM, so that when you either use QuickLook or switch to the Desktop, the notebook can still show what it is in the window. As such, the more files on the desktop, the more data is stored in RAM, which could possibly lead to less RAM space, and run slower.
By properly organizing files, moving them into their appropriate folders, there might be a noticeable improvement in your notebook’s speed
Turn off File Vault encryption
The File Vault allows the user to encrypt every file stored on the MacBook for protection purposes. The encryption (and de-encryption) process entails processor cycles, however.
To turn off this particular feature, just go to System Preferences and then click on the Security and Privacy tab. One can see the File Vault tab. Once there, click the padlock, and type in the admin password and the click Turn off File Vault.
See if that made a positive change in the performance.