Red Line MT-90 75W-90 GL-4 Manual Transmission Lubricant — 1 Quart x2, synchronizer-safe smooth shifting

Red Line MT-90 75W-90 GL-4 is a high-performance manual transmission and transaxle lubricant formulated to protect gears and synchronizers while delivering smooth, predictable shifts.

This MT-90 manual transmission lubricant from Red Line is engineered for gearboxes and transaxles that require GL-4 (and compatible GL-1/GL-3) fluids. It uses a 75W-90 viscosity to provide reliable protection across a broad temperature range, avoid corrosive reactive sulfurs common in GL-5 formulations, and maintain excellent synchronizer friction characteristics so shifting stays crisp and low-notice. The product comes in convenient 1-quart bottles sold as a two-pack for easy service intervals or multi-vehicle maintenance.

What makes MT-90 suitable for manual transmissions and transaxles?

MT-90 is formulated specifically for the challenges of manual gear sets and synchronizers. It balances wear protection with a synchronizer-friendly friction profile, which prevents sticky or notchy shifts and helps extend synchro life. It is recommended where GL-1, GL-3, or GL-4 specifications are called for.

• GL-4 chemistry safe for brass and bronze synchros
• 75W-90 viscosity for stable film strength across temperatures
• Designed to reduce gear wear and extend component life
• Eliminates notchy shifting, improving drivability

How does MT-90 help with shifting performance in cold or hot conditions?

This formula maintains an appropriate coefficient of friction at low and high temperatures, providing predictable synchronizer engagement and quicker gear changes. Drivers notice smoother shifts immediately after fill, and the viscosity choice helps preserve protection during both cold starts and sustained highway runs.

• 75W rating improves cold-flow for easier cold-weather shifts
• 90 high-temperature behavior keeps oil film on gear faces
• Consistent synchronizer performance reduces shift effort
• Stable formulation minimizes viscosity breakdown over time

Which vehicles and applications are appropriate for this oil?

Use MT-90 in manual transmissions, transaxles, and differentials requiring GL-4 (or compatible GL-1/GL-3) lubricant. It’s especially recommended where manufacturers advise against GL-5 due to reactive sulfur content that can harm brass synchros. Check your owner's manual for recommended gear oil viscosity ranges including 75W-90, 80W, or SAE 40 equivalents.

• Manual gearboxes specifying GL-4 or special synchromesh fluids
• Vehicles with brass or bronze synchronizers sensitive to GL-5
• Applications calling for 75W-90, 80W, or SAE 40 viscosity ranges
• Enthusiast and performance cars where shift quality matters

Why choose Red Line MT-90 over generic gear oils?

Red Line has a long reputation for performance lubricants tailored to specific driveline needs. MT-90 is blended to protect gears and synchronizers without the sulfur additives that can attack yellow metals. The formula targets improved component life and a more refined shift feel compared with generic GL-5-heavy gear oils.

• No reactive sulfurs that damage brass synchros
• Engineered synchronizer friction for smoother shifts
• Trusted brand with a history of specialty lubricants since 1979
• Sold in convenient 1-quart bottles, two-pack for service convenience

Who is this for: Red Line MT-90 75W-90 GL-4 MTL is ideal for DIY mechanics, performance-minded drivers, and workshop technicians who service manual transmissions, transaxles, and differentials that specify GL-4 or synchromesh fluids. It's particularly well suited for vehicles with brass or bronze synchronizers where GL-5 oils are not recommended and for anyone who wants improved shift quality and long-term gear protection.