Avoid Grinding Gears with Valvoline Gear Oil

As any go-fast enthusiast will tell you: few things connect man and machine like a smooth-shifting manual transmission. No waiting for an onboard computer to determine how you should drive. The responsibility – and therefore the power – is yours.

While a greater learning curve and less ADAS compatibility has manufacturers shifting away from factory stick shifts, many gearheads still opt for a manual gearbox. That means, they need a quality gear oil to keep it in tip-top operating shape.

What is Gear Oil?

Gear oil is an extremely important lubricant. It’s specifically designed to prevent metal-to-metal contact between the meshing gears in transmissions, differentials, and to a lesser extent, transfer cases.

Unfortunately, most drivers don’t realize the critical role that gear oil plays in a vehicle. Even those who regularly drive a manual transmission may overlook the vital lubricant during scheduled maintenance, as many modern manuals boast gear oil service intervals of 50,000 miles or more.

The fact that so many vehicle owners don’t worry about their gear oil is both a benefit and a burden, says Kwame Duho, Technical OEM Manager at Valvoline. While it’s a testament to the hard work that goes into the oil formulations, it also means many consumers are unaware of the heavy-lifting these light lubricants do on a daily basis.

“A lot of lab work is required to make sure we use the right additives so we can meet the high demands of modern vehicles,” he says. “It’s a balanced art, because you don’t want to sacrifice durability for efficiency gains – and fuel efficiency is the goal for everyone these days.”

Pushing Forward

As manufacturers push for better fuel economy, vehicle parts get smaller. But these smaller parts are asked to do more work, says Duho. “A little engine can now generate as much power as an old V-8. So, these components are working really hard and generating high temperatures,” he explains.

All that extra heat can spell disaster for the delicate gears that live inside a transmission or differential. Plus, churning gears create motion — and motion creates air. Those foaming air bubbles not only wear down metal, but also create unwanted noise during driving.

A quality gear oil will offer features like anti-wear, anti-scuffing, anti-oxidants, and anti-foaming. Together, these properties extend the service of the gear oil to keep it performing at the most optimum levels.

Choosing Gear Oil

Because different automakers use different materials and engineering processes to achieve their goals, Duho says choosing the right gear oil for the right application is really important.

“For example, if you have a synchronizer in your manual transmission, then you need good friction performance and low wear rates, to demonstrate good shift quality and synchronizer compatibility. You also need a good corrosion inhibitor to protect the copper and alloys that are in there, that could be affected by metal-to-metal contact,” he says.

However, some manufacturers use brass as their synchronizer, while others may use bronze. While both are considered “soft yellow metals” (i.e., not steel), different oil additives will affect their performance in very different ways.

Duho recommends drivers always consult the vehicle manufacturer when it comes to selecting a gear oil. This way, they guarantee a correct match. “OEMs designed their vehicle and they know the components intimately,” he says. “Check the manual. Once you figure that out, you can choose the right oil – hopefully Valvoline!”

Valvoline Gear Oils

Valvoline offers a complete line of gear oils intended for a wide range of applications. Duho says the company’s offerings follow a good-better-best approach in order to cover all manufacturer gear oil recommendations.

“We formulate the 80W90 and 85W140 with conventional base oils,” he says. “These represent the ‘good,’ and they meet all the specifications of a GL-5. Then, we also have a full synthetic 75W90.”

Valvoline High Performance Gear Oil

Valvoline High Performance Gear Oil is designed to provide excellent load carrying capacity, extreme pressure properties, anti-foam performance, demulsibility (ability to release water), corrosion protection, and thermal stability protection capability. The company recommends these products for conventional rear axles, and transmissions requiring EP gear lubes under high speed, high load, high torque, and high horsepower conditions.

“Then, you move down to the 75Ws and in order to meet the cold temperature requirements, you need synthetic base oils,” says Duho.

Valvoline Full Synthetic Gear Oil

Valvoline Full Synthetic Gear Oil is a superior sulfur-phosphorus extreme pressure gear lubricant, containing synthetic basestocks and additives to provide excellent performance. Designed to provide excellent extreme pressure protection, load carrying capacity, anti-foam performance, corrosion protection, and thermal stability protection, Valvoline Full Synthetic Gear Oil is recommended for conventional and high-performance applications, for use in axle applications requiring factory-fill or drain-and-fill levels of limited slip performance.

“Again, choice comes down to vehicle manufacturer recommendations,” says Duho. “When they develop the transmissions or axles, they develop it by looking at certain performances. As they reduce size, the gears will be working overtime (because there is less gear oil in there), so they will spec a gear oil so that it has better cold temperature properties, better oxidation or thermal stability.”

Valvoline Synchromesh MTF

For certain GM and Chrysler synchromesh applications, Valvoline offers its Synchromesh Manual Transmission Fluid. This high-performance manual transmission lubricant contains a blend of multifunctional additives, a shear-resistant viscosity modifier, and premium quality base stocks. Designed to provide excellent load carrying capacity, extreme pressure properties, anti-foam performance, corrosion protection and thermal stability protection, this product also provides excellent cold temperature properties without altering synchronizer performance characteristics.

Valvoline recommends Synchromesh MTF for manual transaxles or transmissions where synchronizer performance is vital. The lubricant is fully compatible with components in modern manual transmissions including yellow metals like bronze, copper and brass.

“Formulation-wise, any claim that Valvoline makes on its gear oils has been totally vetted,” says Duho. “What we say in our marketing material, we believe. We have tested it extensively in trials, bench testing, then re-testing to ensure it meets the demand of the customer.”

Changing Gear Oil

How often should a driver change their gear oil? Duho says that depends on driving conditions.

“If you run your car really harshly, then you need really good gear oil properties,” he explains. “For example, if you go off-roading a lot or you tow often, you’re putting a lot of stress on the transmission and differential, so it’s prudent to change these oils pretty regularly – compared to someone who is just driving from home to work.”

However, those who engage in stop-and-go traffic may find their gear oil needs more regular attention. “Every time the vehicle stops, parts of the gear surface are deprived of fluid,” says Duho. “Continuous stopping and starting creates more metal-to-metal contact frequently, compared to the continuous fluid film you would experience when driving longer distances on the highway.”

If you’ve ever changed gear oil, you know it can be a messy job. Thankfully, Valvoline recently launched a squeezable pouch for the FlexFill™ Full Synthetic Gear Oil, ensuring less waste and an easier application.

Gear Oil Substitutions

It’s a common misconception that motor oil can be used in place of gear oil. While this may still hold true for some old rides (like classic Minis), Duho says the DIY swap would spell disaster in a modern vehicle. Even the best engine oil formulations are no match for the small-but-mighty parts in today’s transmissions and differentials.

“The detergents and anti-oxidants in engine oil simply can’t provide the correct synchromesh durability and shift quality needed,” he explains. “If you put engine oil into a modern manual transmission, it’s just going to degrade quickly.”

The API specifications that differentiate gear oils can also cause some confusion.

Often, consumers assume that a GL-5 fluid (say, for a differential) meets the gear oil requirements of a GL-4 application (like a manual transmission), and then thinks the two oils can be used interchangeably.

This is actually not accurate when it comes to synchronized manual transmissions, says Duho.

The main difference between a GL-4 and GL-5 gear oil is the amount of Extreme Pressure (EP) additives. EP additives help protect gear components from high-pressure wear by forming a “sacrificial layer” between the gears’ metal surfaces, explains Duho. “That means, when the gears ride, slide, or roll against each other – instead of shearing metal to metal, they have the additives as a sacrificial layer in between them, so they shear that instead.”

This layer bonds to the metal, and the bonding is really strong. The issue? EP additives typically contain organic sulfur, phosphorus, or chlorine compounds, which can react aggressively toward soft alloys – like those found in a manual transmission’s synchronizer.

Differentials – which don’t use synchronizers – express more load or force, so they need the higher amount of extreme pressure protection that a GL-5 gear oil would provide. However, if a person put that oil into their manual transmission, the bonding would be so great, that as the sacrificial layer peeled off, it would actually take away little bits of the delicate brass or copper synchronizer in the process! A GL-4 gear oil provides a little less extreme pressure protection, so the transmission can reap the benefits of a quality lubricant without suffering any corrosion from the additives.

It’s safe to say that today’s gear oil ain’t your granddaddy’s gear oil.

In order to help manufacturers reach new fuel economy standards, gear oil formulations now have lower viscosities. However, lower viscosity makes the fluid lighter, says Duho, which means the additives need to work harder in order to provide the same amount of protection and durability.

Looking Ahead

Valvoline employs strategic research teams who look at where the market is heading and create new oil formulations to adapt. Anant Kolekar is a performance gear oil formulator at Valvoline who works on one of these strategic research teams. He says that while low viscosities are a major focus, there are other things affecting oil innovations today too, like new transmission materials – and entirely new technology.

“Electric vehicles are exponentially affecting the way we look at transmission oils,” says Kolekar. For example, most commercial EVs operate with a single-speed gearbox. They rely on the electric motor to produce a consistent amount of torque at any given RPM within a specific range. As a result, EVs deliver power instantly – no revving required.

“As governments around the world are putting severe restrictions on emissions and how much fuel cars can use, that puts a lot of demand on transmissions,” explains Kolekar. He remembers a project a few years ago in which the target was to create a gear oil with more than a 50% reduction in viscosity to meet new efficiency needs. “This project is an example of why we need to develop new molecules and new additives just to keep up with customer demand and new technology as it evolves.”

The Right Stuff

Kolekar says in this quest for greater efficiency, the two key parameters are thermal stability and oxidation stability. As transmissions get complicated and work harder, “protecting different components at a lower viscosity [is important],” he says, “but also how to take away heat from the different contacting surfaces like gears, bearings, and motors.”

“And that all comes down to selecting the right base oil and additive packages,” adds Duho.

Luckily, Valvoline has labs around the world working on this exact task. Strategic research teams, like Kolekar’s, are constantly exploring innovative additives and even using unique modeling technology to test out different drive cycles on sample transmissions.

So, the next time you see a buzzy new vehicle with eyeball-popping specs and shockingly impressive fuel economy numbers – think of Duho and Kolekar and all the other gear oil strategists working behind the scenes to keep your ride ridin’ at top efficiency!