Why Your System Needs Gear Oil

October 28, 2022

Mechanical systems are subject to extreme amounts of pressure and heat. Adding gear oil is a must to protect this system from extensive wear and tear. 

But what is gear oil? Simply put, it’s a lubricant designed specifically for high-pressure systems, including:

  • – Gearboxes
  • – Transaxles
  • – Differentials
  • – Transfer cases

You can use gear oil in any vehicle, from bulldozers to gasoline-powered cars to lawn equipment, as long as you choose the right oil for that machine. In this guide, we’re going to tell you everything you need to know about choosing and using gear oil, including some product recommendations we’re happy to share. 



Engine oil and gear oil serve similar functions – both lubricate, protect and cool mechanical systems. But since each type of oil has different additives, they’re not interchangeable. 

Engine oil is designed to lubricate the bearings of your car’s engine and protect it from harmful additives in gasoline. It contains additives like detergents and dispersants, which clean away harmful byproducts from your ignition. Since a car’s combustion engine has an oil pump and lubricates itself with a hydrodynamic film, it doesn’t need the same high-pressure additives as gear oil.

Gear oil is specifically formulated for gearing systems. In addition to serving as a lubricating layer of protection, gear oil removes debris from areas where metal-on-metal contact occurs. It also provides protection against oxidation, rust, copper corrosion and thermal degradation, all of which can harm your gearbox.  

Gear oils contain extreme-pressure additives because gears often experience boundary lubrication, which happens when moving parts wear away the lubricating film between them. Extreme-pressure additives help to maintain this lubricating layer on gears.  



The first step you should take is to check your owner’s manual. If your manual names a specific product or a list of products that work for your car, that’s what you should use. It’s crucial that you use a gear lubricant that works for your car since gear system specifications vary widely from vehicle to vehicle.

The three main factors you should consider when selecting a gear oil are viscosity, base oil type and oil additives. Out of these three, the oil’s viscosity is the most important because it will determine the oil’s resistance to extreme friction. 



Essentially, viscosity refers to the thickness of your oil, which also determines how resistant the oil’s film will be to friction at a specified speed and load.

You should be able to find the ideal viscosity for your car in your owner’s manual. If your manual doesn’t have that information, check with your usual mechanic to find out what they recommend. 

As a rule of thumb, stick to high-viscosity oils for high-pressure, low-speed systems and low viscosity oils for high-speed, low-pressure systems.



Different types of gear oil contain different additives. Additives are chemical compounds that change the properties of the base oil by adding new properties and suppressing undesirable properties. 

For example, extreme pressure additives increase the base oil’s ability to withstand high degrees of pressure.

Other common types of additives include:

  • – Antioxidants
  • – Corrosion inhibitors
  • – Anti-foam agents
  • – Viscosity index improvers
  • – Detergents
  • – Tackiness agents
  • – Metal deactivators



There are three main types of base oil:

  • – R&O: Rust and oxidation oil is helpful for chemical stability, corrosion prevention and foam suppression. It contains the fewest additives out of the three types.
  • – Antiscuff: These extreme-pressure lubricants contain film strength-enhancing additives like sulfur phosphorous, which react with the chemicals on machine surfaces to prevent adhesive wear when boundary lubrication happens. Antiscuff oil is usually best for heavy loads and slow speeds.
  • – Compounded: Typical compounded oils contain a synthetic fatty acid that increases the oil’s lubricity and film strength. Compounded oil is most commonly used for worm gear applications, which require specialized, highly viscous lubricants.



While browsing the different types of gear oil on the market, you might wonder — should you choose a synthetic gear lube or a conventional formula? Is there even a difference between the two?

Conventional gear oil is made from a cocktail of high-quality mineral oils. It’s generally a more economical option than synthetic oils and does the job just fine, but it also tends to contain undesirable compounds like hydrocarbons and nitrogen. These compounds might become an issue because they can enable oxidation within your system, leading to higher amounts of friction and sludge formation.

Synthetic gear grease is higher in purity than natural mineral oil, meaning it’s less prone to oxidation and breakdown. Its molecules are also uniform in size, making them more predictable in action. All Hot Shot’s Secret Gear Oils are synthetic and 100% PAO-based. PAO oils resist shearing and break down, even in the toughest conditions. Plus all our oils are infused with Hot Shot’s Secret patented FR3 Nano Technology which helps increase boundary layer protection and improves film strength for extra protection.

In general, synthetic gear oil is best for extreme conditions, while conventional oil is more of an all-around solution.



Just like with motor oil, it’s essential to regularly change your gear oil. The oil deteriorates over time due to the high grinding levels between metal parts in the gear system, which releases tiny pieces of metal into your oil. This metal debris causes the system to lose lubrication, which can harm your vehicle.

So how often should you change your gear oil? Again, you should check your owner’s manual first. The schedule your manufacturer recommends will be your best bet since that schedule is specific to your car.

Some signs that it might be time to change your oil include:

  • – Unusual burning smells
  • – Whining or grinding noises
  • – Fluid leaks of dark or gritty oil
  • – Illuminated check engine light

If you’re experiencing one or more of these issues, it’s a good idea to check under the hood and see what’s going on.