Red Line MT-85 75W-85 GL-4 Manual Transmission Gear Oil — 1 Quart, Synchro-Safe Protection

Red Line 50504 MT-85 is a 75W-85 GL-4-rated manual transmission gear oil formulated to protect gears and synchromesh while promoting smooth, quick shifts.

Designed for performance-oriented and everyday manual transmissions, this 1-quart bottle of Red Line MT-85 targets vehicles that require GL-4 friction characteristics and brass-safe lubrication. It delivers long-lasting gear protection, helps preserve synchro life, and provides consistent shifting feel even in cooler conditions. MT-85 is widely recommended across various makes, including Nissan, Mitsubishi, Hyundai, Kia, and Quaife-equipped gearboxes.

How does MT-85 improve shifting performance?

MT-85 balances friction and lubricity to minimize harsh engagement and reduce shift effort. Its formulation keeps synchromesh surfaces functioning smoothly so you get crisper, more predictable gear changes, especially during cold starts.

• 75W-85 viscosity for reliable cold-start shiftability
• Controlled friction profile to protect and assist synchromesh
• Stable film strength under load to prevent gear wear

Is this safe for transmissions with brass synchronizers?

Yes—MT-85 is a GL-4-rated oil that avoids the reactive sulfur compounds found in many GL-5 formulations, which can damage brass and bronze synchros. That makes it suitable where manufacturers specify GL-1, GL-3, or GL-4 fluids, and where special synchromesh lubricants are required.

• GL-4 chemistry safe for brass and bronze synchros
• Recommended where special synchromesh fluids are called for
• Reduces synchro wear for extended component life

Which vehicles and applications commonly use MT-85?

MT-85 is popular in a wide range of manual transmissions: from Nissan sports cars like the 350Z/370Z to family sedans and performance boxes in Mitsubishi, Hyundai, Kia, and Quaife-equipped gearsets. It’s a practical choice for enthusiasts upgrading fluids and for routine service when GL-4 is specified.

• Nissan 350Z and 370Z manuals; many Maxima, Altima, Sentra gearboxes
• Mitsubishi Evolution and similar performance-oriented transmissions
• Hyundai and Kia manual transmissions that call for GL-4
• Aftermarket Quaife differentials and synchro systems

How will MT-85 affect maintenance and component longevity?

Using the correct GL-4 fluid helps reduce gear and synchronizer wear, which can extend service intervals and lower repair costs. MT-85’s formulation aims to maintain film strength under pressure while providing friction control, supporting longer synchro life and consistent gearbox feel over time.

• Protects gears from wear under load
• Helps prolong synchromesh life and performance
• Supports reliable shifting across temperature ranges

Who is this for: Drivers and mechanics who need a brass-safe GL-4 manual transmission oil that blends performance and protection—ideal for owners of Nissan 350Z/370Z, many Maxima/Altima/Sentra models, Mitsubishi Evolution, various Hyundai and Kia manuals, and aftermarket Quaife synchro systems. It’s also a strong choice for anyone seeking improved shift quality and longer synchro life without resorting to GL-5 chemistry.