75W90

75W-90 is a multigrade gear oil specification used primarily in manual transmissions, transaxles, and many differentials. The designation consists of two numerals: 75W and 90. The “75W” part describes the oil’s cold-temperature viscosity and low-temperature performance, while the “90” describes its viscosity at high operating temperatures (around 100°C). The multigrade formulation helps the oil provide adequate lubrication across a wide temperature range and improves cold-start shifting compared with single-grade oils.

Base oils can be mineral, synthetic, or blends, and are combined with additive packages that typically include anti-wear and anti-oxidation agents, corrosion inhibitors, and viscosity modifiers. Some 75W-90 formulations include friction modifiers to improve performance in limited-slip differentials; others are formulated without these modifiers to remain compatible with certain LSD types.

Applications and compatibility: 75W-90 gear oils are commonly used in manual transmissions and transaxles in passenger cars and light trucks. They may also be used in certain differentials, depending on the manufacturer’s specification. To determine suitability, consult the vehicle’s owner manual or service information for the required API performance class (often GL-4 or GL-5) and any LSD considerations.

Standards and variations: Many 75W-90 products meet API GL-4 and/or GL-5 specifications, and some brands carry MT-1 or regional equivalents. Availability ranges from mineral-based products to full synthetics and synthetic blends.