Main points
- A lower number, such as 75, indicates that the oil flows more easily at cold temperatures, making it suitable for use in colder climates.
- Use a lower-numbered oil for colder climates and a higher-numbered oil for warmer climates.
- If your vehicle has a gear oil filter, it should be changed at the same interval as the gear oil itself.
Navigating the world of gear oils can be a daunting task, especially when it comes to understanding the cryptic numbers and letters that represent their weight. In this comprehensive guide, we will unravel the mystery behind gear oil weight, empowering you to make informed decisions for your vehicle’s transmission.
The Importance of Gear Oil Weight
Gear oil plays a crucial role in protecting and lubricating the gears, bearings, and other components within your vehicle’s transmission. Its weight, denoted by a combination of numbers and letters, determines its viscosity, flow characteristics, and suitability for specific applications.
SAE Viscosity Grade
The Society of Automotive Engineers (SAE) establishes viscosity grades for gear oils. These grades are expressed as a number followed by the letter “W” for winter. For example, 75W-90 is a common gear oil weight.
The number before the “W” indicates the oil’s viscosity at low temperatures. A lower number, such as 75, indicates that the oil flows more easily at cold temperatures, making it suitable for use in colder climates.
The number after the “W” represents the oil’s viscosity at high temperatures. A higher number, such as 90, indicates that the oil remains thicker at higher temperatures, providing better protection for gears under heavy loads and high-speed operation.
Gear Oil Viscosity Index
In addition to the SAE viscosity grade, gear oils also have a viscosity index (VI). The VI measures the oil’s resistance to thinning out as temperatures increase. A higher VI indicates that the oil maintains its viscosity better over a wider temperature range.
API Service Classification
The American Petroleum Institute (API) classifies gear oils based on their performance characteristics. The API service classification is typically denoted by a letter followed by a number. For example, API GL-5 is a common classification for high-performance gear oils used in heavy-duty applications.
Choosing the Right Gear Oil Weight
Selecting the appropriate gear oil weight for your vehicle is crucial for optimal transmission performance. Factors to consider include:
- Climate: Use a lower-numbered oil for colder climates and a higher-numbered oil for warmer climates.
- Transmission type: Manual transmissions generally require a lower-viscosity oil than automatic transmissions.
- Vehicle load: Heavier vehicles and those that tow frequently require a higher-viscosity oil.
- Manufacturer’s recommendations: Always refer to your vehicle’s owner’s manual for the recommended gear oil weight.
Common Gear Oil Weights
Some of the most common gear oil weights include:
- 75W-90
- 80W-90
- 85W-140
- 90W-140
When to Change Gear Oil
The recommended interval for changing gear oil varies depending on the vehicle and usage conditions. Typically, it is recommended to change gear oil every 30,000 to 60,000 miles or as specified in your vehicle’s owner’s manual.
Signs of Dirty Gear Oil
Dirty gear oil can lead to premature wear and tear on your transmission. Signs of dirty gear oil include:
- Leaking: A gear oil leak can indicate a worn seal or gasket.
- Discoloration: Dark or cloudy gear oil is a sign of contamination.
- Metallic particles: The presence of metallic particles in gear oil indicates wear on transmission components.
What You Need to Learn
Q: What happens if I use the wrong gear oil weight?
A: Using the wrong gear oil weight can lead to decreased performance, accelerated wear, and potential transmission damage.
Q: Can I mix different gear oil weights?
A: Mixing different gear oil weights is generally not recommended as it can alter the oil’s viscosity and performance characteristics.
Q: How can I check my gear oil level?
A: The procedure for checking gear oil level varies depending on the vehicle. Refer to your vehicle’s owner’s manual for specific instructions.
Q: What is synthetic gear oil?
A: Synthetic gear oil is made from synthetic base oils, which offer superior performance and protection compared to conventional gear oils.
Q: How often should I change my gear oil filter?
A: If your vehicle has a gear oil filter, it should be changed at the same interval as the gear oil itself.