You already know printer ink is expensive. Actually, it's one of the priciest liquids you buy. Ounce-per-ounce, even the cheapest ink (about $13 an ounce) costs more than fine champagne.

But here's the real shocker: A lot of that precious material doesn't get onto the paper but ends up wasted.

Consumer Reports found that some printers gobble up a significant amount of ink—50 percent or more—for nonprinting functions such as cleaning print heads.

The extra cost of using a model that soaks up ink for routine maintenance could be as much as $120 a year, the editors estimated.

"We were surprised by the amount of ink some printers used," said Electronics Editor Paul Reynolds.

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Consumer Reports investigated the problem of disappearing ink after readers complained that they weren't getting their money's worth—fewer copies than the magazine projected based on its rigorous tests.

Its engineers suspected the problem was caused by intermittent printing. So, they designed a new test to simulate real-world conditions: print a few pages now and then, and keep the machine off in the meantime.

The revised test protocol was to print 30 pages of text or color graphics intermittently over a three-week period.

In the lab, Consumer Reports put several dozen big-name all-in-one inkjet printers through their paces. While most of the models used most of their ink to print, only a few came within striking distance of using all of it.

Based on this new testing, the researchers verified the cause, documented the difference between models and figured out how to get more pages per cartridge.

"Our tests confirm that it's worth paying attention to how much ink is used for cleaning and maintenance, and to make that part of your buying consideration," Reynolds said.

The worst offenders for wasted ink were the HP Officejet Pro 8600 and the Lexmark OfficeEdge Pro 4000.

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Brother stood out from the pack. All three of its printers tested were consistently frugal with ink when used intermittently. Consumer Reports named the Brother DCP-J140W at $80 a CR Best Buy.

With other manufacturers, the amount of maintenance ink used varied widely, even within brands. For example, the HP Envy series of printers used relatively little ink for maintenance, while HP's Photosmart series used a lot more.

Good news: You don't need to sacrifice performance to save on ink. Several models that were fine performers were also some of the stingiest with maintenance ink.

(Read: "The High Cost of Printer Ink" from the August issue of Consumer Reports)