Red Line 75W90 GL-5 Synthetic Differential Gear Oil - 946ml • 57904

Red Line 57904 75W90 GL-5 Synthetic Differential Gear Oil - 946ml

Full-synthetic Red Line gear oil for suitable open and limited-slip differentials, final drives and hypoid gear applications requiring SAE 75W90 / 80W90 / SAE 90 API GL-5 gear oil.

Red Line 75W90 is an ester-based high-performance gear lubricant formulated for passenger cars, light trucks, competition vehicles and other demanding differential applications. Extreme-pressure additives provide protection for heavily loaded hypoid gears, while the synthetic base stocks provide excellent shear stability and consistent viscosity across a broad operating-temperature range.

The formulation already contains limited-slip friction modifier, making it suitable for many clutch-type limited-slip differentials without requiring a separate additive. Red Line also states that its reduced sliding friction can help lower operating temperature and improve differential efficiency.

This product meets API GL-5 and MT-1 requirements and is also recommended against MIL-L-2105E and SAE J2360. Red Line publishes a wide range of manufacturer-equivalent references, including Mazda 0000-77-80W9-QT.

• Product type: Full-synthetic differential / final-drive gear oil
• Brand: Red Line Synthetic Oil
• Product reference / SKU: 57904
• Viscosity grade: SAE 75W90
• API service class: GL-5 / MT-1
• Additional standards: MIL-L-2105E / SAE J2360
• Container size: 946ml / 1 US quart
• Primary use: Open and limited-slip differentials / hypoid final drives
• Limited-slip compatibility: Friction modifier already included
• Viscosity at 100°C: approximately 16.1 cSt
• Viscosity at 40°C: approximately 108 cSt
• Viscosity index: approximately 161
• Pour point: approximately -45°C
• Mazda reference listed by Red Line: 0000-77-80W9-QT
• Restriction: Not recommended for most synchronised manual transmissions

Fitment advice: Use where SAE 75W90, 80W90 or SAE 90 API GL-5 differential gear oil, or one of Red Line's specifically published equivalent specifications, is required. The formulation contains limited-slip friction modifier, but the vehicle or differential manufacturer's fluid specification should take priority.

Important transmission note: Although this is a gear oil, Red Line does not recommend it for most synchronised manual transmissions because its friction characteristics can be too slippery for correct synchroniser engagement. For a synchronised manual gearbox, use the appropriate Red Line manual transmission lubricant where specified.

Other items to consider: When servicing a differential, you may also want to consider replacement drain and fill plug washers, differential seals, breather components and related drivetrain service parts where required.

Useful tools / consumables: Fluid transfer pump or filling bottle, drain pan, suitable sockets or spanners, torque wrench, gloves, workshop towels and brake cleaner for external clean-up.

Difficulty guide: DIY Difficulty: Moderate. Differential oil replacement is generally straightforward, but the correct lubricant specification, fill level and drain/fill procedure must be followed.

Why Red Line? Red Line Synthetic Oil is known for high-performance lubricants, fluids and additives developed for demanding road, track and motorsport use. Red Line products are chosen by enthusiasts and workshops for their focus on protection, thermal stability, shift quality, friction control and application-specific performance.

What’s in the bottle: One 946ml / 1 US quart bottle of Red Line 75W90 GL-5 Synthetic Gear Oil.

Service notes: Drain the existing differential lubricant and refill to the manufacturer's specified level. Because limited-slip friction modifier is already included, additional modifier should only be added where specifically required to correct clutch chatter or meet the differential manufacturer's requirements.