Your prnter is lying to you:
The study by TÜV Rheinland looked at inkjet efficiency across multiple brands, including Epson (who commissioned the study), Lexmark, Canon, HP, Kodak, and Brother. They studied the efficiency of both single and multi-ink cartridges. Espon's printers were among the highest rated, at more than 80 percent efficiency using single-ink cartridges. Kodak's Easyhare 5300 was panned as the worst printer tested, wasting 64 percent of its ink in tests. TÜV Rheinland measured cartridge weights before and after use, stopping use when printers reported that they were out of ink.