ShelfYears

Does gear oil expire?

It has a stated shelf life rather than a spoilage date: Chevron rates its gear oils at 60 months sealed, and ExxonMobil gives the same 5 years to oils and greases generally.

Updated

Gear oil
Sealed
5 years
Opened
2–3 years
ADDITIVE DROP-OUT
Degraded performance

Sealed: 5 years Tier 1

Chevron's product shelf-life table puts Havoline Gear Oil SAE 80W-90 and SAE 85W-140 at 60 months each. ExxonMobil arrives at the same place from the other direction: 5 years for oils and greases, when stored properly in the original sealed containers.

After opening: 2–3 years Tier 3

Valvoline's rule for any chemical that has been opened is no longer than 2–3 years, depending on storage. Gear oil is thick enough that the base oil barely notices, but the extreme-pressure additives it carries are the reason the bottle exists, and they are the part that ages under air.

How to tell it's gone off

  • Separation into layers, or a distinct band sitting apart from the body of the oil.
  • Sediment in the bottom that stays put after the bottle is shaken.
  • A significant change in color or odor against a fresh bottle of the same grade.
  • A noticeable change in texture — oil that has gone thicker, grainy or stringy.
  • Read the lot or date code on the bottle against the 5-year window.

If you use it anyway

Degraded performance

Old gear oil is a specification problem rather than a hazard. Chevron stops at 60 months and ExxonMobil recommends the same 5 years for sealed containers; past that, neither maker stands behind the additive package. The base oil is still oil. What is no longer guaranteed is the extreme-pressure chemistry the grade was sold for, and a bottle showing separation or a settled layer that will not go back in is one to leave alone.

Why it goes off — ADDITIVE DROP-OUT

Gear oil is a heavy base oil carrying a large sulfur-phosphorus additive package — the chemistry that lets gear teeth run under pressure without welding themselves together. In a bottle that has stood untouched for years those additives can settle or separate out. ExxonMobil's own list of signs that a stored lubricant has deteriorated is excessive oil separation, a significant change in color or odor, and a noticeable change in texture.

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 terms: the original sealed container, in a sheltered environment under good housekeeping conditions, at typical ambient temperatures. An unheated shed that swings between freezing and baking is outside what the 5-year figure assumes.

Do not pour old gear oil down a drain.

Sources