With every run this code returns a different result with the difference being between .1 - .2 s Any ideas why ?

That is how stuff works, there is variability in everything -- the harddisk spins, sometimes it takes more time to read a file, sometimes less, sometimes its retrieved completely from cache ... think of timing a run/sprint/race with a finger-clicked-stopwatch -- sometimes you run faster, sometimes timer/coach fingers/thumbs slower -- its why runs are averaged, its like statistics or something :)