Don't mix dye with pigment ink. Sometimes the results are bad for the head. I tested this with an HP45 just to see. Huge CLOG that even a snap and fill can't budge. Obviously it was the mixture of type of inks. So be careful . If you decide todo it at least get rid of one completely first.
Most newer single cart black cartridges are pigment based. Older ones were dyebased before pigment based technology was affordable to put in a consumer level printer. Any triple-color photo cartridge that has Photo Cyan, Photo Magenta, and Photo Black are going to have dyebased black. The new Black #02 cartridge is dyebased.
Generally, really older ones are dyebased, newer business/deskjet/officejet cartridges are pigment if it's an all-black cartridge, and photo printers will have dyebased ink. There's enough variation in this that you should always look up the cartridge number and find the specifics - for instance, most of the PhotoSmarts that still take the head-on-carts take both pigment all-black cartridges and photo black cartridges. So there's no way to know for sure without finding out about that exact model.