ShelfYears

Does grease expire?

Yes — Mobil rates its greases at 5 years in the original sealed container, and ExxonMobil is blunt that the number stops applying the moment the lid comes off.

Updated

Grease
Sealed
About 5 years
Opened
Not rated once opened
OIL BLEED & ADDITIVE LOSS
Degraded performance

Sealed: About 5 years Tier 1

Mobil's industrial storage FAQ puts it plainly: the recommended shelf life for Mobil-branded greases is 5 years when stored properly in the original sealed containers. ExxonMobil's aviation team gives the wider picture — about 3 years is the industry average for aviation greases, while Mobilgrease 33 and 28 are rated for up to 10. Formulation, not brand loyalty, is what moves the number.

By manufacturer — the disagreement is information
Brand Sealed window
Mobil industrial greases 5 years sealed
Aviation greases, industry average About 3 years
Mobilgrease 33 and 28 Up to 10 years

After opening: Not rated once opened Tier 1

ExxonMobil withdraws the number outright: "Once a container is opened, the grease should be used as soon as possible to avoid potential contamination or degradation," and "the listed shelf life recommendation for a grease is no longer applicable once the container is opened." An open tub is on shop air — dust, moisture and whatever came off the last tool that went into it.

How to tell it's gone off

  • A puddle of free oil on top when the lid comes off — Mobil's static oil bleed. A film is normal; a pool in an old tub is not.
  • Noticeably harder or softer than a fresh cartridge of the same grade — Mobil flags a consistency change of more than 25%.
  • A clear change in color or smell from what the label and a new container show.
  • A change in texture: grainy, stringy or crusted where it used to be smooth.
  • Grit, rust flecks or standing water in a tub that has sat with a loose lid.

If you use it anyway

Degraded performance

Old grease is a performance problem, not a damage one. ExxonMobil's language for a grease past its window is a decrease in the additives that provide wear protection, oxidation stability and structural stability — it still greases, with less of the protection you paid for. Mobil's list of deterioration signs is the same shape: separation, consistency, color, odor, texture. You get a job done to a lower standard and sooner than you planned, not a wrecked bearing on the spot.

Why it goes off — OIL BLEED & ADDITIVE LOSS

Grease is oil held in a soap thickener, and the two slowly part company on the shelf. Mobil calls the free oil that shows up on top static oil bleed and says some of it is normal and necessary. Underneath that, the additive package fades: ExxonMobil says that as a grease passes its shelf life you may see a decrease in the performance additives that provide wear protection, oxidation stability and structural stability. The grease still looks like grease long after it has stopped being the grease on the label.

Every page here commits to one of four states — Harmless · Degraded performance · Equipment damage · Safety issue. How the verdicts work.

How to store it

ExxonMobil's rule set: containers indoors, in a dry, cool, clean place, with normal storage temperatures between 0°C and 40°C (32°F to 104°F). Keep the cartridge in its box and the lid on the tub, and treat an opened container as one that no longer carries a published window — ExxonMobil says to use it up rather than store it.

Sources