Lower texture quality consumes more GPU? Dafuq?

[Determined]

So, after changing my texture quality in GTA IV from High to Medium to achieve a satisfactory fps of 50-70 instead of a modest 30-60 & restarting the game, it won't run anymore, instead it gives me a "GTA IV FATAL ERROR: Out of video memory...." error, does anyone know why the fuck this happens? I'm using Icenhancer 2.1 & yes, I can still run the game with high texture quality, but that's not what I want.

[Sasha Dotterkletch]

those weird things that rockstar has. in max payne 3 with my old 9500 gt, with directx9 and low textures, 5-10 fps. directx10 with medium high settings, 15-40 fps (super playable fps)