Is 75W90 a synthetic oil?
75W-90 is not inherently synthetic. It is a viscosity rating used for gear oils, especially in manual transmissions, and products labeled 75W-90 can be mineral-based, synthetic, or synthetic blends. The exact composition depends on the manufacturer and the product line.
What 75W-90 Really Means
The numbers in 75W-90 refer to viscosity. The "75W" indicates good flow at cold temperatures, while the "90" indicates thicker oil at higher operating temperatures. This rating is defined by the SAE (Society of Automotive Engineers). The "W" stands for winter-grade viscosity. In gear oils, the 75W-90 designation tells you how the oil behaves across temperature ranges, but it does not specify whether the oil is synthetic or mineral-based.
Types of 75W-90 Oils
The market offers three main formulations of 75W-90 gear oils. Below are the broad categories you may encounter.
- Mineral-based 75W-90: Made from refined crude oil with additive packages. Usually the least expensive option.
- Full synthetic 75W-90: Based on synthetic bases (such as PAO or esters) with specialized additives for performance in extreme temperatures and under high loads.
- Synthetic blend 75W-90: A mix of mineral and synthetic base oils, offering some synthetic benefits at a lower price than full synthetics.
Regardless of the base oil, all three deliver the same 75W-90 viscosity. The differentiator is performance characteristics, temperature range, longevity, and price driven by the base oil and additives.
How to Tell If Your 75W-90 Is Synthetic
To determine whether a specific 75W-90 product is synthetic, look for clear labeling and technical documentation from the manufacturer.
- Check the product label for terms like “Synthetic,” “Full Synthetic,” or “Synthetic Blend.”
- Review the product data sheet or MSDS on the manufacturer’s website for base-oil details (e.g., PAO, ester) and whether the formulation is synthetic.
- Verify the listed specifications (such as API GL ratings) to ensure compatibility with your vehicle’s manual/transfer case or transmission requirements.
- Consider the price and marketing language; synthetic oils generally cost more than conventional mineral oils.
- Ask a parts counter or service advisor, or search the retailer’s listing to confirm whether the product is synthetic.
In practice, the label and the manufacturer’s technical data are the most reliable sources. If in doubt, consult your owner’s manual or contact the vehicle’s dealership or lubricant supplier for the exact specification your transmission requires.
Choosing the Right 75W-90 for Your Vehicle
Choosing the correct 75W-90 depends on vehicle design, climate, and operating conditions. Modern manuals often specify a GL-4 or GL-5 gear oil, and some older manuals have different requirements. Synthetic oils tend to offer better high-temperature stability and longer drain intervals, while mineral oils may be sufficient for older or lightly loaded transmissions and typically carry a lower price.
Differences Between Full Synthetic and Synthetic Blend in Gear Oils
Full synthetic gear oils usually provide superior cold-weather performance, oxidation resistance, and temperature stability. Synthetic blends aim to balance performance with cost, offering some synthetic benefits without the higher price tag. The best choice depends on the vehicle’s design, its operating environment, and the maintenance schedule recommended by the manufacturer.
Summary
In short, 75W-90 is a viscosity grade used for gear oils and does not by itself indicate a synthetic oil. Oils labeled 75W-90 can be mineral-based, fully synthetic, or synthetic blends. To know whether a specific product is synthetic, check the label and the manufacturer’s technical data. Always match the oil type to your vehicle’s manual specifications and operating conditions. When in doubt, consult a trusted mechanic or the vehicle’s dealer for guidance.
What is 75W90 gear oil used for?
75W90 gear oil is used in automotive and heavy-duty applications, such as differentials (including limited-slip types), non-synchronized manual transmissions, and transfer cases. It is designed to protect gears and bearings under high-pressure and shock-loading conditions in a wide range of temperatures, making it suitable for both heavy hauling and extreme driving environments.
Common uses
- Differentials: Provides protection for hypoid rear differentials, especially under high torque, high speed, and heavy load conditions. It is also often used in limited-slip differentials.
- Manual Transmissions: Ideal for non-synchronized manual transmissions where extreme pressure protection is needed.
- Transfer Cases: Protects the gears in transfer cases for four-wheel drive vehicles.
- Heavy-Duty Applications: Used in on-highway and off-highway vehicles such as trucks, buses, construction equipment, and mining vehicles.
Key benefits
- Extreme pressure protection: The "EP" (extreme pressure) additives protect against wear and scuffing under heavy loads.
- Wide temperature performance: The "75W" (winter) rating indicates good flow in cold temperatures, while the "90" viscosity grade ensures protection in high temperatures.
- Thermal stability: Resists breakdown and oxidation at high temperatures, which extends component life and oil change intervals.
- Wear protection: Reduces wear and tear on gears and bearings, including protection against corrosive and shock load wear.
Is 75W90 synthetic?
Description. PROLAB's 75W90-S and 80W90-S products are synthetic oils for industrial gearboxes with exceptional properties: they outclass standard oils by their performance and durability.
Is Valvoline 75W90 synthetic?
Valvoline Flex Fill 75W-90 Full Synthetic Gear Oil 1 QT Squeeze Pouch.
How to tell if gear oil is synthetic?
Unfortunately, there is no reliable way of differentiating between mineral and synthetic in the field.
