How to save color ink printing B/W or Grayscale

I have a Canon Pixma MP780 printer and it has 5 cartridge, 3 color, 1 black dye, and 1 black pigment. The black pigment is used for text, while the dye is used for photos.

How can i force the printer to use the Pigment black only for b/w prints?
Like printing webpages online? Or b/w photoshop/illustrator artwork?

I called canon support twice, and both reps said that this can't be done. Even with the grayscale option enable in the printing preference. The printer will still use a composite of the color cartridge to simulate grayscale tones, mostly the blue ink will be used in neutral gray. The pigment base ink will only be used on ASCII text they said, anything else would be a composite gray if grayscale is enabled or just color.

So the Rep said i am better off just printing in color and setting it as draft mode. Since printing in grayscale would use more colored ink to simulate the dark graytones than just using color from the start. Hmm....

There has to be a way right? like forcing it to halftone and dither? Im not sure. Anyone with any ideas on this or thoughts?

I went into my printer defaults and told it b/w was the default. Do that, take out the color cartridges, and see if it still prints.

Canon CS Rep said that even if the preference option is set to Grayscale (no b/w option for pixma780), there is still color ink being used to create the gray tones. It mixes composite of the color ink to create those neutral gray tones.

Can't take out the color cartridge, printer wont print, and if it does, the printhead would burnout because liquid ink is required to cool the nozel on the printhead. That was the Canon explaination. I guess it is a good safety feature.

When you say B&W prints, do you mean continous tone for display, or just a record of what was onscreen? I'm confused 'cause you also say "Like printing webpages online? Or b/w photoshop/illustrator artwork?"
My color cartridge has been empty for weeks & it prints what I need in B&W Draft mode.
XP = Properties> Print Advisor / Fast print B&W mode.

Well for photoshop and illustrator it would be lineart. For webpage it would be a mix of b/w text and grayscale graphics.

What printer do you have? My Pixma780 doesn't have b/w mode, only grayscale option. Also, the Canon Rep said that leaving the ink cart empty would likely damage the print head nozzle. BEcause those nozzle is heated up to vaporize the ink to the paper, but if there is no ink in the cartridge it won't cool down the nozzles. Canon Rep also said my pixma780 would refuse to print if any ink cartridge is empty.

Printer is a Cheapie Canon ip1500 that came free with my computer. I only print draft with it as Costco gets all my photo print business.

Wonder if this issue can be fixed with a new driver to allow B/W printing (pigment only) instead of Grayscale(used color ink to create gray tones)