HP 910XL cyan · XL

Buying the HP 910XL cyan instead of the standard 910 cyan is the single biggest saving available on the printers it fits. The XL covers 825 pages at $18.99, so 2.30 cents a page, while the standard manages 315 pages for $13.99, or 4.44 cents. That is 48 percent off the running cost for $5.00 more at the till, and it beats what the same step up saves on the black, which is 35 percent.

Seven machines take it, all from the same HP OfficeJet generation: the 8012, 8015e, 8020, 8025, 8025e, 8035 and 8035e. Every one of them is on our firmware lockout list. HP ships this generation with Dynamic Security, and the models ending in e were offered HP+ at setup, which is a permanent commitment to Original HP ink if it was accepted. Before buying compatible 910XL tanks, work out which position your printer is in, because an enrolled HP+ machine will never take them and there is no way back out of that enrolment.

At 2.30 cents a page this colour is also cheaper to run than the black in the same family, which sits at 5.45 cents. Printing a document in colour on these machines genuinely costs less than printing it in greyscale.

The tank itself holds only ink. The print head stays in the printer, so streaky or missing colour points at dried ink in the machine rather than at anything you can buy. When the printer says it cannot detect a cartridge you have just installed, the usual causes are the protective tape still over the outlet or a tank that has not seated with a click.