Longines · Longines L888

Longines HydroConquest, Spirit and Legend Diver power reserve: inside the L888

The Longines HydroConquest, Spirit, Conquest, Legend Diver and Master Collection all run on versions of the L888, which lasts about 72 hours off the wrist in current form. That's three full days, enough to cover a weekend with time to spare.

Updated September 2026 · Based on manufacturer specs, published reviews and watchmaker/owner reports

Watches that use the L888

If you bought a three-hand automatic Longines in the last few years, it almost certainly has an L888 inside. The name covers a family of versions (L888.2, .4, .5 and .6), all made by ETA exclusively for Longines. The suffix matters: the .4 and .6 are COSC-certified chronometers, and the older versions have less reserve than today's 72 hours.

Not every Longines has it. Quartz HydroConquests, GMT models (the L844), chronographs (the L898 and others) and some small ladies' sizes use different calibres.

Specs at a glance

History and where it came from

Until the late 2010s, Longines's automatic three-handers mostly used the ETA 2824-2 with its 38-hour reserve. Monochrome reports that the HydroConquest and the Legend Diver both ran on 2824-based movements before the switch. The L888 changed that. The first version, the L888.2 (ETA A31.L01), arrived in 2017, and by 2018 the Legend Diver had it too.

ETA's approach was the same one it used for Tissot's Powermatic 80: slow the beat and fit a bigger mainspring. The L888 runs at 3.5 Hz instead of 4 Hz, which alone stretches the reserve, and the L888.2 was rated 64 hours. Unlike the Powermatic, it's built on the thinner, higher-grade ETA 2892 architecture rather than the 2824, which is why Longines can put it in slim dress watches like the Master Collection.

The next step was the silicon balance spring. The L888.4 (COSC-certified) arrived with the Spirit in 2020, and the non-certified L888.5 followed; both were initially rated 64 hours. From about 2021, Longines quoted 72 hours for the L888 in the HydroConquest, and the COSC-certified L888.6 in the 2023 Legend Diver 39 is also 72 hours. Today the whole family is listed at 72 hours with a silicon spring.

Accuracy in the real world

Only the chronometer versions come with a number. The L888.4 in the Spirit and the L888.6 in the Legend Diver 39 are COSC-certified, which means -4/+6 seconds a day when tested as bare movements. For the L888.5 in a HydroConquest, Conquest or Master Collection, Longines doesn't publish a rate.

Owner reports on watch forums are generally positive, with many HydroConquest and Conquest owners describing single-digit daily rates. As always, there's variation, and some watches need regulating. The 3.5 Hz beat is marginally less stable in theory than 4 Hz, but the difference is small next to the effect of regulation and wear pattern.

The silicon balance spring is the bigger deal day to day. According to Monochrome, it gives the current L888 about ten times the magnetic resistance ISO 764 requires, roughly 600 gauss. That makes it much less likely than an old 2824-based Longines to start running fast after sitting near a laptop or speaker.

Reliability and servicing

The L888 is built on ETA's well-understood 2892 layout, and there's no widely reported systemic weakness. Longines backs its automatic watches with a 5-year warranty.

• Brand service. Longines services it through the Swatch Group network, and a movement exchange instead of a rebuild is common.
• Independents. Parts for Swatch Group's exclusive calibres are restricted to its own network and certified watchmakers. An independent can often service an L888, but finding one who will may take some asking.
• Silicon spring. A silicon hairspring can't be tweaked by hand the way a metal one can, so a damaged one is replaced rather than repaired.

Quirks worth knowing

• Check the year, not just the name. A 2018 HydroConquest and a 2024 one both say "L888", but the older one was rated 64 hours without a silicon spring. The full calibre number is in the manual and on Longines's spec sheet.
• Slightly slower sweep. At seven beats a second the seconds hand is a touch less smooth than a 4 Hz movement. Most people won't notice.
• A lot of spring to fill. From stopped, give it 30 or more turns of the crown rather than relying on a morning's wear.
• The date. It has a quickset date. As with most date movements, don't set it late at night. Here's why.

How it compares

• Powermatic 80 / Hamilton H-10: the Swatch Group siblings. 80 hours at 3 Hz, but based on the thicker 2824 and found in cheaper watches.
• ETA 2892 / ETA 2824: what Longines used before. 4 Hz, but only about 38 to 42 hours of reserve.
• TAG Heuer Calibre 5: the common choice at a similar price, but a conventional 38-hour, 4 Hz movement.
• Oris Calibre 400: a five-day reserve, a silicon escapement and a 10-year warranty, in watches that cost a little more.
• Tudor MT5602: 70 hours, COSC and a silicon spring, one price step up.

Living with the 72-hour reserve

Seventy-two hours is exactly three days, and that covers the classic problem case. Take your HydroConquest off at 7pm on Friday and it's still running at 7pm on Monday, so a weekend with a different watch won't stop it. A Spirit worn Monday to Thursday can sit out Friday, Saturday and Sunday and be ready for the week.

It won't cover a week away, and the 72 hours assumes a full spring. A Legend Diver that only got an afternoon's wear before going into the drawer may stop on Sunday. If you rotate two or three Longines, it's worth knowing which ones need a wind. Watch Winder counts down this 72-hour reserve for each watch you own and reminds you before it stops. To check a specific weekend, try the "Will my watch stop?" calculator.

If you own an older, 64-hour HydroConquest or Spirit, budget for a day less. Friday evening to Monday morning is fine; Friday to Monday evening is not.

Verdict

The L888 is a big part of why Longines is such an easy recommendation in the Swiss mid-price bracket. It's slim enough for a Master Collection, tough enough for a HydroConquest, and in current form gives you three days of reserve and a silicon hairspring, with COSC certification in the Spirit and Legend Diver 39. The trade-offs are the Swatch Group ones: parts go only to its own network, and the version history is confusing enough that you should check which L888 you're buying. Buy a recent one and it's hard to fault.

FAQ

How long does a Longines HydroConquest run off the wrist?

A current HydroConquest with the L888.5 runs for about 72 hours, or three days, from a full wind. Models from 2017 to 2020 with the L888.2 were rated 64 hours.

Does the Longines Spirit hack?

Yes. The L888.4 in the Spirit stops the seconds hand when you pull the crown to set the time, and it can be wound by hand.

How accurate is the Longines Spirit?

The Spirit's L888.4 is a COSC-certified chronometer, so it has passed testing at -4/+6 seconds a day. Owners generally report rates well within that.

Is the Longines Legend Diver a chronometer?

The 39 mm no-date Legend Diver uses the COSC-certified L888.6. The 42 mm date version uses a non-certified L888 version.

Why did my Longines Conquest stop over the weekend?

It probably wasn't fully wound. The 72-hour figure is from a full spring, and light wear may leave it well short of that, so wind it 30 or more turns by the crown before a long rest.

Is the Longines L888 an ETA movement?

Yes. It's made by ETA exclusively for Longines, based on the ETA A31.L family, which uses the ETA 2892 architecture. Longines-specific changes include the slower 3.5 Hz beat, the longer reserve and a silicon hairspring.

What's the difference between the L888.2, L888.4, L888.5 and L888.6?

The L888.2 was the 2017 original with a 64-hour reserve and no silicon spring. The L888.5 adds a silicon hairspring, and the L888.4 and L888.6 are COSC-certified versions; current examples are all rated 72 hours.

Sources

• Longines: Conquest L3.830.4.02.6 product page
• Monochrome: The redesigned 2026 Longines HydroConquest
• Monochrome: Longines Conquest 2023 collection
• Monochrome: Longines Legend Diver 39mm No-Date with calibre L888.6
• Monochrome: Longines Legend Diver Black PVD with calibre L888.2

Keeping it running

• On an average day an automatic gains roughly 4 hours of reserve per hour on the wrist, so about 18 hours of wear fills the Longines L888. Desk days charge more slowly.
• Most automatics can also be wound by the crown. If yours has stopped, a few dozen turns gets it going before you put it on.
• Off the wrist it stops about 72 hours after it was last full. Stopped sooner?
• On a watch winder, start at about 650 turns per day, both directions. Winder settings for every movement.
• If it does stop, don't set the date between 9pm and 3am. Check if it's safe.

Other 70-hour movements

Never let it stop

Watch Winder counts down the reserve of every watch you own and reminds you before one stops. It already knows the Longines L888: type your watch's name and the reserve fills itself in.

Manufacturer's published figure. Real reserve varies with the watch's age and service; check your manual.