Gear Synth 75W90 GL-5

It looks like you're referring to a type of gear oil, specifically 75W90 GL-5, and mentioning a brand called "Gear Synth." Gear oil is a lubricant specifically designed for use in differentials, manual transmissions, and other gear systems in vehicles and machinery. The "75W90" and "GL-5" are specifications that provide information about the oil's viscosity and performance characteristics.

Here's what those specifications mean:

75W90: This is a viscosity rating for the gear oil, indicating how thick or thin the oil is at different temperatures. The "75" represents the oil's viscosity at lower temperatures (cold start or winter conditions), and the "90" represents the viscosity at higher temperatures (normal operating conditions). Lower numbers indicate thinner oils at cold temperatures, which can provide better cold-start lubrication.
GL-5: This is a gear oil specification established by the American Petroleum Institute (API). GL-5 oils are designed to provide high levels of protection for hypoid gear systems, which are commonly found in automotive differentials. They offer enhanced load-carrying capacity and extreme pressure (EP) protection.
As for the brand "Gear Synth," it seems to be the manufacturer or brand name of the gear oil you mentioned. It's important to choose a reputable and trusted brand when selecting lubricants for your vehicle or equipment to ensure proper performance and protection.

Before using any specific gear oil, make sure to check your vehicle or machinery's manufacturer recommendations to ensure that the chosen oil meets the required specifications and is compatible with the intended application. Using the right type of gear oil can help extend the life of your gear systems and provide optimal performance.