HP using only colour ink

I have an HP Photosmart C4270. Whenever I print text, gray, or black, the printer only uses the colour cartridge to make said colour. The colour cartridge is empty before you know it, and the (cheaper) black one is never in use. This even happens when I tick 'Print text in black' in LibreOffice...
Does anyone know what to do about this? Is this a tactic by HP to let those not willing to pay for an OS pay extra for ink? Does anyone know who to contact to request a change in this policy?