Does windows really need 15% of free space at all times?

I often read in tune-up \ speed up tips that windows need at least 10 or 15% of system drive free at all times, otherwise it’ll slow down, is that true?

I currently have 5 gb free (out of 60) on my system drive and everything seems to work fine…pretty fast too…mostly…

Does that tip about 15% free space have something to do with windows auto pagefile control? Cuz I have set mine to 2Gb min\max (I have 8 GB of Ram).

its probably for temp files, windows updates, pagefile etc.