Can unopened gear oil still be used after 10 years?
3 Answers
Unopened gear oil cannot be used after 10 years. Function of gear oil: Gear oil mainly refers to the lubricating oil for transmissions and rear axles, which differs from engine oil in terms of usage conditions, composition, and performance characteristics. Its primary functions include lubricating gears and bearings, preventing wear and rust, and assisting in heat dissipation for gears. Introduction to gear oil: Gear oil should possess excellent anti-wear and load-carrying properties, along with appropriate viscosity. Additionally, it should have good thermal oxidation stability, anti-foaming characteristics, water separation performance, and rust prevention capabilities. Classification of gear oil: Gear oil is divided into two categories: automotive gear oil and industrial gear oil. The former is used for lubricating various manual transmissions and gear drive shafts in vehicles; the latter is employed in lubricating gear mechanisms across industries such as metallurgy, coal mining, cement production, and chemical processing.
I've seen quite a few engine oils and gear oils that have been stored for many years. Honestly, ten years is indeed too long. Even if the bottle hasn't been opened, the chemical additives in the oil may deteriorate and separate. The lubricating effect of the base oil will be greatly reduced after oxidation, and its low-temperature fluidity will also deteriorate. The worst part is when some additives precipitate into sludge, making it impossible to mix evenly during use. Some old-school mechanics used to say that well-sealed oil could last twenty years, but modern formulations typically have a shelf life of three to five years. If you insist on using such aged oil, not only does the risk of gear wear increase significantly, but you could also end up damaging your transmission – that would be a huge loss.
Last time during a car repair, I witnessed the tragedy of adding decade-old oil into the differential. It started screeching after just five kilometers, and when opened up, it was full of brown sludge. Fresh gear oil is transparent amber, but the decade-old stuff had turned soy-sauce black. The key additives had long since separated, with sediment at the bottom like sesame paste. When changing the oil, we also found the seals had corroded and swollen from the old oil—this is definitely not where you should cut corners. The labor cost for a transmission repair could buy twenty barrels of fresh gear oil. Nowadays, when I encounter such customers, I just pour out the old oil right in front of them to kill any thoughts of reusing it.
