Red Line 75W90 GL-5 Synthetic Differential Gear Oil - 3.78L • 57905

Red Line 57905 75W90 GL-5 Synthetic Differential Gear Oil - 3.78L

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

Red Line 75W90 is an ester-based high-performance gear oil 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 strong 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 exceeds API GL-5 requirements and is also listed against API MT-1, 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: 57905
• Viscosity grade: SAE 75W90
• API service class: GL-5 / MT-1
• Additional standards: MIL-L-2105E / SAE J2360
• Container size: 1 US gallon / approximately 3.78L
• 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 / 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 manufacturer's fluid specification should always take priority.

Important transmission note: Although this is a gear oil, Red Line does not recommend 75W90 GL-5 for most synchronised manual transmissions because the friction characteristics can be too slippery for correct synchroniser engagement. For GL-4 manual transmissions, use the appropriate Red Line MTL, MT-85 or MT-90 product instead 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, 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 correct oil specification, fill level and drain/fill procedures 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 1 US gallon / approximately 3.78L container 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 friction modifier is already included, additional limited-slip additive should only be added where specifically required to correct clutch chatter or meet the differential manufacturer's requirements.