If your printer will print with the cover opened (maybe this is one reason why many won't), you'd be amazed at how much colour ink they waste on printing black or nearly black content.
The principles of Inksaver were demonstrated far better by an old driver replacement I used once - Superprint on an old Deskjet 550C - It had the following tricks:
GCR - Grey component replacement: Where a colour has a certain amount of C, M and Y in it, an equal amount of black is substituted. The effect is a slight reduction in saturation of dark colours, and a much less wet print.
Depletion - reduces the maximum inking of solid areas: Worked very well, as standard, the Deskjet could even leave an ink puddle in solid black areas. Over-inking black and solid colour seems to be common, giving a very dense output, but wasting ink.
Dot gain control: Allowed tuning for dot spread on different paper types
Dither matrix adjustment: Various ways to reduce unwanted patterning or clumping.
Between those, I got a picture on some glossy card that I'd been told (by the guy I bought it from) was no good for photo, as the ink runs.
The situation now is that:
They DO waste colour ink in the black - Inksaver can apparently filter that out.
They DO over-ink dark areas.
At the lowest Ink saving settings, it's generally just removing the waste.
Pre adjusting the source material may be another possibility, as only solid black can be over-inked, so lightening th source a little may have a similar effect as using an ink saver program, though the colour in black issue would not be corrected.