I have a Dell colour laser printer and my black ink is running low, but what's more surprising is that my colour ink is also running low. I am almost always printing plain text documents with hardly any colour at all (maybe blue for a Word heading), so why would yellow and magenta have gone down, too?
Question: Why/how would a laser printer use colour ink when printing plain black and white documents?
Most printers use a combination of black toner/ink and color toner to print documents. The reason is it aids in a number of things, like:
Depending on your printer, you may have the option to force it to use only the black ink/toner cartridge for greyscale printing, but you may notice a loss of quality or smoothness in fonts. For instance, Brother calls this setting "Mono".
Another option that might be available is if your printer allows to print when a cartridge is empty or missing. If your printer supports it, you can simply remove the color cartridges and print only using the black one.
Most printer manuals will include a disclaimer that printing in black and white does not mean that only the black cartridge will be used.