ULTRA 1PLUS SAE 75W-90 Synthetic Gear Oil GL-4 - Year-Round Protection

In this review of ULTRA 1PLUS SAE 75W-90 Synthetic Gear Oil GL-4, the bottom line is simple: this fluid is aimed at vehicle owners and mechanics who need a durable, year-round gear lubricant that supports smoother shifting and longer gear life. The product's single biggest selling point is its advanced synthetic formula that forms a stable lubrication film to reduce wear under heavy pressure, so those maintaining transmissions, axles, or transfer cases will appreciate its combination of thermal stability and limited slip additive benefits.

Key Features

• Advanced 75W-90 GL-4 Formula: Premium synthetic base oils provide superior thermal stability and cleanliness for reliable protection under high loads.
• Anti-Scuffing and Friction Modifiers: Special additives reduce metal-to-metal contact and help prevent scuffing in gears running under extreme pressure.
• Year-Round Viscosity: Meets SAE J306 requirements so the oil maintains appropriate flow and protection across a wide temperature range.
• Enhanced Gear and Bearing Longevity: Forms a robust lubrication film that reduces wear and minimizes deposits, extending component life and lowering maintenance needs.
• Leakage Prevention and Limited Slip Support: Formulated to reduce leakage and includes a limited slip differential additive package for improved performance in diff applications.
• Optimal Temperature Resilience: Retains adequate lubrication properties in both low and high temperatures for consistent operation.

Who It's For

This gear oil is best for DIY mechanics, professional shops, and drivers who service front-wheel drive gearboxes, differentials, and transfer cases that call for an API GL-4, SAE 75W-90 oil. It suits vehicles operating in varied climates because the synthetic base maintains viscosity and protection from cold starts to high operating temperatures.

Those who should look elsewhere include owners who specifically require API GL-5 formulations or specialty gear fluids specified by some manufacturers, and anyone needing an oil with a manufacturer-specific certification not listed here. If a vehicle manual explicitly requires a different spec, follow the OEM guidance.

Pros & Cons

Pros

• Smooth shifting and quieter operation reported in transmissions and transfer cases, improving driver experience.
• Good value for money with quality synthetic base oils and protective additives for extended component life.
• Effective year-round viscosity and temperature resilience for varied climates and driving conditions.

Cons

• Some customers note mixed impressions of lubricant color and appearance, which does not affect performance but may be subjective.

Specifications

Product Type	SAE 75W-90 Synthetic Gear Oil
API Classification	Exceeds API GL-4
Viscosity Standard	Meets SAE J306 requirements
Key Additives	Anti-scuffing, friction modifiers, limited slip package
Primary Benefits	Thermal stability, reduced wear, leakage prevention
Volume	12 QTS

Our Verdict

ULTRA 1PLUS SAE 75W-90 GL-4 is a practical choice for most owners needing a reliable, synthetic gear oil that balances protection, smooth shifting, and year-round performance. It represents solid value for transmissions, axles, and transfer cases where API GL-4 is specified, offering extended component life and reduced maintenance risks.

Frequently Asked Questions

Can this oil be used in limited slip differentials?
Yes, the formulation includes a limited slip differential additive package to support those applications.

Is this suitable for cold climates?
Yes, it meets SAE J306 viscosity requirements for year-round performance, maintaining flow and protection in low temperatures.

Does it meet API GL-5?
No, this product is formulated to meet and exceed API GL-4 standards; check your vehicle manual if GL-5 is required.