85W140

85W-140 is a grade of gear oil used primarily in automotive differentials and manual transmissions. The designation comprises two numbers: 85W refers to the oil’s low-temperature performance (the W stands for winter), and 140 refers to its viscosity at high operating temperatures. This combination yields a relatively thick oil at typical operating temperatures, suitable for high-torque, high-load gearsets.

Most 85W-140 gear oils are formulated as mineral-based, synthetic, or blends and include extreme-pressure additives, anti-wear agents, and corrosion inhibitors. Many products meet API GL-5 specifications, and some carry MT-1 ratings for use in manual transmissions that require that standard. They are generally not recommended for transmissions that specify GL-4 or for engine use.

Typical applications include rear axles with hypoid gears, limited-slip differentials, and certain heavy-duty manual transmissions, especially in trucks, SUVs, and off-road vehicles. They are chosen for high temperature stability, load-carrying capability, and reduced wear in demanding conditions. In very cold climates, the high high-temperature viscosity can slow fluid flow on startup, so some users prefer lighter grades.

Users should consult the vehicle owner’s manual or the differential’s specification to ensure compatibility. Using an unsuitable viscosity or standard can affect shifting, noise, and gear wear. Oils labeled 85W-140 are common in aftermarket replacements, but some newer vehicles require lighter grades such as 75W-90 or 80W-90.