Ultra1Plus SAE 75W-90 Synthetic Gear Oil GL-4 (3 Pack QT)

In this review of the Ultra1Plus SAE 75W-90 Synthetic Gear Oil, the bottom line is simple: this three-quart pack is aimed at drivers and mechanics who need reliable year-round gear lubrication that reduces wear and keeps shifts quiet. The reviewer found the product best for automotive axle gears, transfer cases, and manual transmissions where an API GL-4 fluid is specified, with the single biggest reason to buy being its combination of synthetic base oils and anti-scuffing additives that form a stable film under extreme pressure.

Key Features

• Advanced 75W-90 GL-4 formula: Premium synthetic base oils provide superior thermal stability and keep gear internals cleaner over time.
• Year-round viscosity: Meets SAE J306 viscosity requirements so it performs consistently in cold starts and high operating temperatures.
• Anti-scuffing protection: Special friction modifiers reduce metal-to-metal wear during heavy loads and repeated shifting.
• Extended gear and bearing life: Forms a robust lubrication film that minimizes deposits and reduces long-term maintenance needs.
• Leakage prevention and limited slip support: The formulation helps reduce leakage and includes a limited slip differential additive package for smoother limited-slip operation.

Who It's For

This gear oil is well suited for owners of cars, trucks, and SUVs with manual transmissions, differentials, or transfer cases that specify an API GL-4 lubricant and require SAE 75W-90 viscosity. It is also appropriate for technicians servicing older or high-mileage FWD gearboxes where improved shiftability and reduced noise are desired.

Those who should look elsewhere include owners who need an API GL-5 or specific manufacturer-specified gear oil not compatible with GL-4 chemistry, and customers who require a fluid with a clearly different additive slate for extreme off-road hypoid gears. If a vehicle manual calls for a different spec, follow the maker's recommendation.

Pros & Cons

Pros

• High-quality synthetic base oils offer thermal stability and reduced deposits.
• Improves shiftability and reduces transmission and transfer case noise for many users.
• Includes additives for limited slip differentials and minimizes leakage in service.

Cons

• Not suitable where API GL-5 or other manufacturer-specific gear oil is required.
• Some users report mixed impressions of slipperiness and color, so aesthetics and feel may vary by application.

Specifications

Our Verdict

The Ultra1Plus SAE 75W-90 Synthetic Gear Oil in this three-pack is a practical choice for drivers and mechanics needing a dependable GL-4 lubricant that improves shift feel and protects gears and bearings. It offers solid value through extended component life and year-round performance, but buyers should verify GL-4 is appropriate for their specific axle or transmission requirements.

Frequently Asked Questions

Is this oil suitable for limited slip differentials?
Yes, the formulation includes a limited slip differential additive package intended to support limited-slip operation.

Can it be used in very cold climates?
Yes, it meets SAE J306 viscosity requirements for year-round performance, so it maintains adequate lubrication in low temperatures.

Is this compatible with GL-5 gearboxes?
No, this product exceeds API GL-4 and is not formulated as a GL-5 replacement; check your vehicle manual for the correct spec.