Which ink does the Canon PIXMA G3270 use?

The PIXMA G3270 is a refillable tank printer, so it does not take cartridges at all. It fills from four GI-21 bottles: GI-21BK black, GI-21C cyan, GI-21M magenta and GI-21Y yellow, poured into tanks on the front of the machine.

The arithmetic is not close to any cartridge model. A GI-21BK is rated 6000 pages for $13.00, which is 0.22c a page, and each colour bottle is rated 7700 pages for $12.00, or 0.16c. A complete set of four is $49.00. For a sense of scale inside our own catalogue, Canon's PIXMA TS3720 needs a $55.00 pair of XL cartridges to print 300 pages, while $49.00 of bottles here prints 6000 black pages and more than that in colour. Per page the difference on black is about 38 times.

One detail that catches people out: on this printer colour is cheaper than black. Each colour bottle covers 7700 pages against 6000 for the black, at a lower price, so 0.16c against 0.22c. Printing everything in greyscale to save money is a cartridge habit and it does nothing useful here.

There is no firmware authentication and no chip to authenticate, which removes the compatible versus original question in its usual form. The question that takes its place is about ink quality, and it deserves more attention than it usually gets, because pigment and dye formulations that were not designed for these printheads are what cause the blockages tank printers are otherwise very good at avoiding. The head on a G series machine is a component of the printer, so the downside of a bad bottle is a repair rather than a wasted cartridge.

Tank printers fail differently from cartridge printers and the habits are worth learning. Do not let a tank run dry, because air drawn into the line is much harder to clear than ink is to top up, and refill when the level reaches the lower line rather than when printing stops. Print at least a page in colour each week, since these machines reward regular use and punish months of standing idle. Before moving the printer, check that the ink stopper or transport lock is set, as a tank machine tipped in a car is a genuine mess. And treat the level you see through the window as the truth, because it is an actual sight of the ink rather than a counter estimating what it thinks you have used.