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The Difference Between GL-4 and GL-5 Gear Oil

The Difference Between GL-4 and GL-5 Gear Oil

The main difference between GL-4 and GL-5 gear oils is in the level of extreme-pressure (EP) additives.

It’s really very simple. They are not interchangeable and GL5 didn’t replace GL4.

by Eddie Yorkman,|July 5, 2022

If you’ve ever purchased gear oil, or spent any time looking at gear-oil specifications, you have undoubtedly come across the API GL-4 and GL-5 specifications. You may have wondered, what is the difference between GL-4 and GL-5 gear oil? Where can I buy GL-4 and GL-5 gear oil?

Severity – Hypoid gears vs Helical

The American Petroleum Institute (API) classifies gears using GL ratings, ranging from GL-1 to GL-5. Higher GL rating numbers represent more severe applications; GL-1 is the least severe and can usually be satisfied with a motor oil, while GL-5 is the most severe GL rating.

EP additives

The main difference between GL-4 and GL-5 gear oils is in the level of extreme-pressure (EP) additives. EP additives effectively protect gears by providing a sacrificial layer on gear surfaces; these additives are essential for protecting gears operating under heavy loads and extreme temperatures. A typical GL-5 gear oil provides about twice as much EP additive in its formulation compared to a GL-4 gear oil.

Where are GL-4 and GL-5 gear oils used?

GL-4 gear oils are typically recommended for spur and helical gears found in manual transmissions and transaxles operating under moderate speeds and loads.

GL-5 gear oils are typically recommended for hypoid gears in automotive axles operating under high-speed, high-load conditions.

What type/weight gear oil should I use?

For top protection and performance, it is best to consult your owner’s manual/Shop manual for the manufacturer’s recommendation. There, you will find both the specified viscosity (75W-90, 75W-140, etc.) and specification (API GL-4, API GL-5, API MT-1, etc.) recommended for your application. Almost all hypoid gear sets require GL-5 due to the need for significant extreme-pressure protection.

Note the 2nd number is the KEY weight under operating temperatures and conditions. 990, 110, 140, 250, etc..  For example our 75W-80 covers and overlaps the recommendations where 80W-90, 85W-90 are written.

What’s the best gear oil for my vehicle?

AMSOIL SEVERE GEAR® Synthetic Gear Lube excels in protecting gears and bearings from the rigors of severe-service operation. By design, it resists breakdown from high heat, preventing acids and maintaining a barrier to prevent metal-to-metal contact while conditioning seals. Its wax-free construction also improves cold-flow properties, improving fuel economy and cold-weather performance.

• Superior film strength
• Controls thermal runaway
• Protects against rust and corrosion
• Helps reduce operating temperatures
• Maximum efficiency
• Long oil, seal and equipment life
• Flexible easy-pack for clean, fast installation

SEVERE GEAR is recommended in differentials, manual transmissions and other gear applications requiring an API GL-5 gear oil. It can also be used in axles where an API GL-4 lubricant is recommended.


How To Protect Your Snowmobile Engine

How To Protect Your Snowmobile Engine

_by David Hilgendorf|September 6, 2023

Manufacturers are designing today’s sleds to deliver unprecedented power and performance, so snowmobile enthusiasts can push the boundaries even further. Two-stroke snowmobiles are meant to be ridden hard, but aggressive riding and running your machine at wide-open throttle all day takes its toll on the engine.

Some models use turbocharging to produce extreme horsepower, but turbos also create intense heat and pressure with the potential to damage the engine. In these extreme conditions, deposits can form on the turbo bearing, pistons and exhaust power valves, reducing engine power and causing engine wear. 

AMSOIL INTERCEPTOR® Synthetic 2-Stroke Oil is designed to handle the challenging engine conditions created by high-performance sleds. To evaluate its performance, we installed INERCEPTOR in a Ski Doo* 850 Etec* Turbo R and ran it on our dyno for 30 hours, simulating a full season of mountain riding.

After testing, we tore down the engine and examined the parts. The synthetic base oils and advanced additives in AMSOIL INTERCEPTOR Synthetic 2-Stroke Oil prevented deposits and wear, keeping parts clean and helping to deliver maximum power and engine life.

AMSOIL INTERCEPTOR Synthetic 2-Stroke Oil is specifically designed for maximum performance in all makes of two-stroke snowmobiles, including Arctic Cat, Polaris and Ski-Doo, helping enthusiasts spend more time riding and less time performing maintenance. It is compatible with most two-stroke oils and its low-smoke, low-odor properties help ensure you enjoy every ride.


We’re so confident in the performance of AMSOIL INTERCEPTOR® Synthetic 2-Stroke Oil that if you run it exclusively in your current-model-year or newer sled, we’ll cover engine repairs for up to two years or 5,000 miles (8,000 km) in the unlikely event of an engine failure under our RUNS ON FREEDOM® LIMITED SNOWMOBILE WARRANTY.



Bryce Menzies Conquers the Baja 1000

Bryce Menzies Conquers the Baja 1000

_by Lindsay Tousignant | December 6, 2023

Bryce Menzies has conquered the Baja 1000 peninsula in multiple race lengths of 250, 400 and 500 miles. Winning these races has already cemented his name if the off-road world, but most notably missing from that list is the longest race, both distance and ongoing, the Baja 1000.

Running the full length of the peninsula for the 25th time in the race’s 56-year history, this year’s 1000 started in in La Paz, Baja California. For the first time in the race’s history, the course ran from south to north, ending in Ensenada. Encompassing 1,311 miles, this race was also the second longest in the history of the event.

The course embodied all that desert racing typically offers, straight dirt passes, coastline stretches, rocky climbs and washes, some of which had seen a radical transitioned since Hurricane Norma rocked the southern end of the peninsula earlier this year. Even though this marked the second longest 1000 in the race’s history, the times seen were relatively fast given the smoother terrain.

Check out Bryce, Andy and Tavo pre-running the course:


Teamed up with drivers Andy McMillin and Gustavo “Tavo” Vildosola, Menzies took the the first 525 miles of the race. He then handed off the Mason AWD Ford Raptor Trophy truck over to Red Bull teammate McMillin for the next 400 miles. McMillin then handed the reigns off to hometown hero Vildosola, who drove the remaining 385 miles to the finish in Ensenada.

The trio finished the SCORE Baja 1000 in 22 hours, 35 minutes and 33 seconds, taking the checkered flag. Menzies earned the official win as the registered race entrant and is only the 10th racer to earn a SCORE Baja Triple Crown, having won the San Felipe 250, Baja 500 and Baja 1000. Menzies also took home the SCORE season championship.

“It took me over 10 years to win the SCORE Baja 1000. To win the second-longest SCORE race in history feels pretty special.”
– Bryce Menzies

Menzies uses AMSOIL products to ensure his race trucks can handle extremely harsh desert racing conditions.

Next up, Menzies is setting his sights on Hammertown and gearing up for the Can-Am UTV Hammers Championship during King of the Hammers, Jan. 25 through Feb. 3, 2024.




GM dexos R Raised the Motor-Oil Bar for High-Performance Engines

GM dexos R Raises the Motor-Oil Bar for High-Performance Engines

AMSOIL Signature Series outperformed before the GM motor oil specification.
Try the 5W-50 Corvette oil available here in Sioux Falls.

The GM dexos R spec applies to modern high-performance cars like the Corvette.

_by Brad Nelson |January 30, 2023

Reposting this past article on our Signature Dexos R 0W-40 and 5W-50. They’re huge sellers in our Omaha location but want to get the word out about the supply here in Sioux Falls.

GM recently launched a new motor oil performance standard with its proprietary dexos R motor oil specification. Dexos R denotes 0W-40 and 5W-50 motor oils that can withstand the rigors of high-speed and high-load conditions created during high-performance driving. As of now, the specification only applies to high-performance engines used in Corvettes and Camaros.

Modern engines with high power density, forced induction, multi-point fuel injection, cylinder deactivation and emissions systems are driving demand for more advanced lubricants. High-performance vehicles push those technologies to another level, requiring a motor oil that can protect components operating in extreme heat and high-load conditions.

Testing is complete and AMSOIL Signature Series already outperforms the dexos R specification. The dexos R icon will be added to Signature Series 0W-40 and 5W-50 packages.

The GM dexos R motor oil specification applies to modern high-performance Corvettes and Camaros.

AMSOIL has pushed lubricant technology to new levels since 1972 when AMSOIL 10W-40 Synthetic Motor Oil became the first synthetic motor oil in the world to meet American Petroleum Institute service requirements. Since then, we have never stopped pushing ourselves to develop more-advanced formulations. The result? We continue to produce the best motor oils on the market.

Stop in and try the 5W-50 “Corvette” oil and discover the performance improvement! Or really the one oil which lets the engine operate to it’s potential!


47073 98th St. Sioux Falls.

AMSOIL Hybrid Motor Oil Protects Hybrid Engines

AMSOIL Hybrid Motor Oil Addresses Hybrid Engine Challenges

_by Johnny Gage |Dec 7th, 2023

Your Maintenance Choices should match the Motives of Hybrid Engine ownership

Hybrid vehicles are designed to improve fuel efficiency and reduce emissions. They combine an internal combustion engine powered by traditional fuels with an electric motor powered by batteries. The electric motor is used to propel the vehicle from stops and for low-speed driving and the gasoline engine takes over powering the vehicle at higher speed and recharges the batteries.  

Hybrids are projected to be 18% of cars on the road by 2035 and roughly half of all hybrid owners identify themselves as automotive enthusiasts. These are drivers searching for modern technology and premium products, who are also committed to maintaining their own vehicles, maximizing safety and reliability, and saving money. 

Hybrid engine challenges – You mean they didn’t do any long term studies??

So often new engine technology requires specific lubricant needs but the call to the manufacturers for a new specification usually lags the issues after issues are discovered.

Hybrid vehicles endure a unique set of challenges due to frequent starting and stopping of the engine. Intermittent operation of combustion engines makes them especially vulnerable to corrosion.

The Key Issue: The infrequent use and instant load  before the engine has had time to warm up creates a situation where the engine cannot evaporate condensation inside the block. This causes rust, greater wear and reduces efficiency. Cooler cylinders can also cause incomplete combustion, increasing the likelihood of unburnt fuel leaking into the crankcase and contaminating the motor oil. It happens all the time and can be mitigated! 

Often the lubricant requirements for these vehicles unique situations are beyond what is available off the shelf at your auto parts store. Not to mention that lower standard of oil you get with the “A Year of Free Oil Changes” or vats at the quicklube.  Not so with AMSOIL!!

Additionally, motor oil needs to flow quickly to critical components every time the engine engages, which is problematic when the engine is constantly cold due to being idle. Hybrid engines are also required to engage quickly under high-load operation to assist the electric motor and must be able to rapidly reach increased engine speeds.

Hybrid engines require high-quality oil that resists moisture, flows properly before it reaches operating temperatures and resists oxidation once it heats up.  

Hybrid solution

AMSOIL 100% Synthetic Hybrid Motor Oil is specifically engineered to address the unique demands of hybrid electric (HEV) and plug-in hybrid electric (PHEV) engines, with a boosted dose of dispersants and inhibitors to help prevent condensation-related corrosion and maintain optimal engine performance. Its robust viscosity combats the negative effects of fuel dilution and maintains consistent and optimal flow of oil to key engine components at low temperatures, ensuring rapid protection at startup.  

AMSOIL 100% Synthetic Hybrid Motor Oil (0W-20 and 0W-16) is API Licensed & ILSAC Licensed and is recommended for service intervals of 15,000 miles or 1 year in normal service. It is a premium upgrade over vehicle manufacturer-branded motor oils, delivering purpose-built protection that extends oil drain intervals and maximizes hybrid performance, fuel economy and engine life. Follow the owner’s manual recommendation for severe service intervals. 

AMSOIL 100% Synthetic Hybrid Motor Oil is tailored to the unique challenges presented by hybrid vehicles, making it an excellent choice for hybrid owners looking for an upgrade in hybrid engine protection.