I got an old macbook, 2009 unibody running Sierra. Have max ran for the 2.26GHz model of 8GB. Now I use my machine for work so quite bit open at present: Firefox 4 tabs Chrome 3 tabs Thunderbird iMessage Skype Dropbox The machine used to use 4.3GB ram if checked with HW monitor in utilities. Now it is reading 5.14GB ram used. Biggest use is firefox at 531MB closly followed by two chrome helper entries at just under 500MB I have plenty of ram to cope with this but, why would the ram creep up in space of about a week. Machine is shut down and goes home in my bag every nite, then taken back to work in morning. As said plenty of ram but same apps and pages open.