Difference Between GL-4 and GL-5 Gear Oil?
2 Answers
The differences between GL-4 and GL-5 gear oil lie in their oil properties and acidity levels. Below are the specific distinctions: Oil Properties: Firstly, GL-4 is a medium-duty gear oil suitable for differential gears, transmission gears, and steering gears. GL-5, on the other hand, is a heavy-duty gear oil designed for extremely harsh operating conditions, such as those found in differential gears and rear axle gears. Acidity Levels: GL-5 gear oil contains more sulfur than GL-4, resulting in nearly double the acidity. Consequently, it naturally has stronger corrosive properties.
When it comes to the difference between GL-4 and GL-5 gear oils, the key lies in the additive types and application scenarios. GL-4 is mainly used for manual transmissions, especially those with synchronizers, as its additives are relatively mild, containing fewer sulfur-phosphorus compounds to avoid corroding the copper alloy surfaces of synchronizers. On the other hand, GL-5 is designed for differentials and rear axle gears, particularly limited-slip differentials, as it is packed with extreme pressure additives to provide more wear-resistant protection against high-impact loads. Mixing them can cause serious problems: using GL-5 in a transmission can damage the synchronizers, leading to rough shifting, while using GL-4 in a differential may wear out the gears. It’s also crucial to match the viscosity grade, such as 75W-90, as specified in the vehicle manual. Every time I help friends check their cars, I emphasize this—choosing the wrong oil can skyrocket repair costs and even shorten the vehicle’s lifespan. Additionally, environmental considerations matter: recycling used fluids during oil changes helps reduce pollution. In short, understanding these details helps avoid common pitfalls and ensures smooth vehicle operation.
