The color toners on my printer are emptying even though I only print using the "grayscale"

[Molokon]

I bought a HP LaserJet pro 4303 four months ago and I've been noticing how the G, C and Y toners are depleting slowly over the course of time, even though I exclusively print using the "grayscale with only black option". The printer is off most of the time since I only turn it on when I'm going to print some word doc, like every two or three days a week, so everytime it is turned on it always do a little quick autocheck I think, wich I read can use a tiny bit of the toner in order to verify everithing is ok, but I don't think that it should be that much to drop the toner levels to 80 in that amount of time.

[Repairatrooper]

Toner will slowly deplete because built in image quality maintenance routines such as automatic calibration will use a small amount of toner, even if you never print color. It is unlikely that you can turn these automatic maintenance routines off. Purchasing a color printer when you only print black and white is never a good purchasing decision.