Try following Epson's recommendation.  They designed the printer to use
Epson Durabrite ink.

Epson printers basically use the same head design whether they use
pigment or dye colorant inks.  The main differences are in the firmware
(which determines how often the heads are run through cleaning cycles,
how much ink is used, etc) and some software issues which have been
related to the how the colorants react to different paper types.

The cartridges may or may not be different. Pigment inks usually also
use a resin ink base meaning they need to be better protected from air
and oxygen.  Pigment ink cartridges tend to be without sponges, but with
sophisticated air exchange systems but dye inks aren't as critical.

Durabrite inks are more clog prone than dye inks, so using dye inks will
probably help to keep the printer heads running better.  Yes, the
pigment inks are more Durable overall, and waterproof, they also give a
sharper image on plain (bond) paper.

If possible I would avoid mixing the inks in the cartridge.  Although
Epson dye inks and pigment inks all use the same solvents, they differ
enough to potentially lessen the value of the output.

Art

If you are interested in issues surrounding e-waste,
  I invite you to enter the discussion at my blog:

      http://e-trashtalk.spaces.live.com/