Redline 75W140 GL-5 Gear Oil Quart

Redline 75W140 GL-5 Gear Oil (Quart)

This Redline 75W140 gear oil is a fully synthetic differential oil built from polyol ester base stocks, so it holds up under the kind of heat and load that breaks down conventional gear oil. It meets API GL-5, GL-6, and MT-1 specifications, along with MIL-L-2105E and SAE J2360. Because of that broad spec coverage, it suits both hypoid and non-hypoid gear sets across a wide range of differential designs. It also already includes friction modifiers suited to clutch-type limited-slip differentials, so most LSDs won’t need any extra additive on top.

Because the ester base stock is so slippery, we don’t recommend this Redline 75W140 gear oil for manual transmissions or transaxles. That same slipperiness can cause synchro mesh issues and rough shifting, so Red Line built it specifically for differentials instead.

Shear Stability and Long-Term Protection

Compared with conventional and other synthetic gear oils, Redline’s shear stability holds up for longer and resists oxidation better. As a result, you get better differential efficiency, longer drain intervals, and less wear on the gears themselves over time. That added stability matters most in differentials that see sustained high loads, such as towing, off-roading, or track use, where oil temperatures climb well above what a standard differential sees on the street. Because of this, many owners choose 75W140 specifically for hard-working setups rather than everyday commuting. However, it’s still a great fit for anyone who simply wants stronger long-term protection.

Typical Properties:

• API Service Class: GL-5+
• SAE Viscosity Grade: 75W140
• Viscosity @ 100°C: 27 cSt
• Viscosity @ 40°C: 192 cSt
• Viscosity Index: 191
• Pour Point: -45°C / -49°F
• Brookfield Viscosity: 1300 poise @ -40°C

This quart bottle suits a top-up or partial refill depending on your differential’s capacity. Check your workshop manual first, or get in touch if you’re not sure how much oil your diff holds. For the full technical data sheet, see Redline’s official product page.