swa66 - 11:18 pm on Feb 10, 2013 (gmt 0)

Then a few days ago I found one for PNGs that reduced file sizes by a whooping 80% without any loss of quality

I'll take your word that you got it 80% smaller, but I refute the "without any loss of quality" with vigor. As that's simply not going to happen unless it's an extremely simple image and stored really poorly. What I presume it should say is that's it without all too much loss of quality - but not without *any* loss of quality.
And then "all too much" becomes subject for debate...

png-8's can seem on first looks quite fine it you reduce the number of colors they can contain but there is a lot of quality loss in that process even if it might not be all too obvious on first looks.