Red Line MT-90 75W90 GL-4 Synthetic Gear Oil - 1 Quart

Red Line MT-90 75W90 GL-4 Synthetic Gear Oil - 1 Quart

Optimized Synchronizer Performance and Yellow Metal Protection

Restore the precision to your gearbox with Red Line MT-90. This 75W90 GL-4 gear oil is the most popular choice for manual transmissions in Toyota, Nissan, Mazda, Mitsubishi, and many other imports. Formulated with polyol ester base stocks, it provides exceptional film strength and thermal stability, ensuring your gears remain protected even under the high-heat conditions of track days or spirited canyon runs. Because it lacks the reactive sulfurs found in most GL-5 fluids, it is completely safe for brass, bronze, and copper synchronizers, preventing the long-term chemical wear that leads to grinding and transmission failure.

What’s Included in the Box:

- (1) 1 Quart (0.946L) Bottle: Standard neck design compatible with most common fluid pumps.

The Red Line Advantage

- Synchronizer Harmony: Specifically balanced friction levels allow synchronizers to lock up quickly, reducing shift effort and eliminating gear clash.

- Safe for Yellow Metals: Formulated without the aggressive sulfur additives found in GL-5 oils, ensuring your brass synchros don't corrode or "thin out" over time.

- Ester-Based Stability: Provides an unshearable oil film that maintains its 90-grade protection even at extreme operating temperatures.

- Superior Cold Shifting: Stays fluid in freezing temperatures, allowing for smooth shifting from the moment you pull out of your driveway.

- High-Heat Endurance: Resists thermal breakdown and oxidation, keeping your transmission internals clean and extending the life of your seals.

Product Specifications

- Part Number: 50304

- Viscosity Grade: SAE 75W90

- Standard: API GL-4, GL-3, GL-1, MT-1

- Viscosity at 100°C: 15.6 cSt

- Viscosity Index: 177

- Flash Point: 250°C / 482°F

- Pour Point: -45°C / -49°F

Precision Tip: MT-90 is a GL-4 fluid, meaning it is intended for manual transmissions and transaxles. It does not have the extreme-pressure additives required for most hypoid differentials (which usually require GL-5). If you are servicing a vehicle like a Miata or a 240SX, you will likely use MT-90 in the gearbox and Red Line 75W90 GL-5 in the rear differential. Most manual gearboxes require between 2 and 4 quarts for a full service.