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

Written by Charleen

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.

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Signature Series Beyond Their So Called Clean

Written by Charleen

Signature Series cleans up the competition

In general, the higher an oil’s TBN, the better its ability to neutralize contaminants such as combustion by-products and acidic materials. Higher TBN oils neutralize a greater amount of acidic material, which results in longer oil life and cleaner engines.

TBN levels decrease as the oil remains in service. When the level reaches a point where it can no longer protect against corrosion, the oil must be changed.

The TBN Test

The Total Base Number Test (ASTM D2896) uses a series of chemical reactions to measure the alkaline additives in a motor oil. We recognize the value of formulating motor oils with high TBN, and AMSOIL Signature Series Synthetic Motor Oil features the highest TBN of the oils tested.

AMSOIL Signature Series is fortified with a heavy treatment of detergent additive and it delivers 30% more acid neutralizing power1 than Mobil 1, and 36% more than Royal Purple, helping engines to stay cleaner, longer.

The AMSOIL Advantage

AMSOIL synthetic lubricants feature a large dose of quality additives that consistently deliver high TBN for the life of the oil. They neutralize acidic contaminants and keep them in suspension to maximize engine protection. AMSOIL lubricants use detergent and dispersant additives to significantly reduce sludge and carbon deposit formation. In the Total Base Number Test (ASTM D2896), AMSOIL Signature Series 5W-30 Synthetic Motor Oil demonstrated the highest TBN of the oils featured in the test, helping it deliver reliable protection for extended drain intervals. One thing the test doesn’t show is our detergent lasts longer. You can see that for yourself when you pull your own oil analysis.

Aftermarket Additives – Did you know?

Just by adding your aftermarket oil additive meant to help with “something”, these additives are used because the user believes it offers an additional attribute which the base motor oil does not offer. With AMSOIL you never need to do this. Anything offered on the market was reviewed often decades ago and if it offers some advantage it will be in the AMSOIL product. If not you risk neutralizing additives such as the detergents which make up the largest part of the price of AMSOIL other than the base oil.

There are several additives which took decades of knowledge to get them to perform together without nullifying the benefits. That’s what aftermarket additives do, they often make a good oil worse than bad. After the additive is added you may have just been better off getting your oil at the dollar store or just using the used oil out of your sisters old Saturn.  (Assuming it still runs because she didn’t use any of these caustic additives)..

Research the brand and even their address

Note – research the company you buy the additive from. One very big one which in the 60’s had their name on Indy cars, etc has been on the FTC’s warning site more than once and has actually been bought and sold no less than 6 times. Each time it becomes a totally different product. Others actually do some good  but at the same time are causing a greater negative in the oil somewhere else.

1Based upon independent testing of Mobil 1 Annual Protection Full Synthetic 5W-30, Royal Purple High Performance 5W-30 and AMSOIL Signature Series 5W-30 in ASTM D2896. Oils purchased 05/03/18.

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Amsoil Diesel Fuel Additives Best Choice For Increased Fuel Lubricity

Written by Charleen

Our Diesel Fuel Additives Will Save Your Fuel System and Add Performance

Diesel fuel additives are the most overlooked motor maintenance item next to motor oil. An essential product that must be added to every tank. Many diesel drivers mistakenly think a fuel lubricant is okay every other tank.

New diesel owners are not being told this critical information from the dealership. 

Adequate diesel fuel lubricity is essential for protecting the highly engineered components in modern diesel engines, particularly high-pressure common-rail (HPCR) engines, which are subject to increased wear and deposits that interfere with an optimum spray pattern, reducing power and fuel economy. Many diesel owners add two-stroke oil to their fuel for added lubricity. AMSOIL delivers a better solution that provides additional benefits.

Amsoils diesel fuel additive selection

ULSD Provides Less Lubricity

Diesel fuel has traditionally had high lubrication properties, but the desulfurization process that allows fuel to meet modern ultra-low-sulfur diesel (ULSD) requirements also strips it of organic compounds responsible for lubrication. Although the ASTM D975 standard for diesel fuel provides a minimum level of lubricity, it’s not as much as the Engine Manufacturers Association (EMA) has called for.

To meet government mandates for reduced emissions, nearly all diesel fuel sold in North America is ULSD, which contains a maximum of just 15 ppm sulfur, compared to traditional diesel fuel that contained up to 5,000 ppm prior to EPA regulations taking effect in 2006. ULSD is also compatible with modern exhaust treatment devices, such as diesel particulate filters (DPF), that also help reduce emissions.

The Two Stroke Oil Remedy

Because lost fuel lubricity and the expenses associated with fuel-pump and injector replacements are serious concerns among diesel enthusiasts, some have adopted the practice of adding a little two stroke or 2 cycle oil to the fuel to replenish the lost lubricating properties. While this is generally a safe practice, it’s not recommended. Because all two-stroke oils are different, it’s a guessing game regarding how much oil is required to achieve a lubricity benefit. Using too little may not provide any benefit, while using too much may violate EPA laws regarding ash content.

The Superior Remedy: AMSOIL Diesel Fuel Additives

The best way to increase fuel lubricity is to use a fuel additive designed specifically for this purpose, like AMSOIL Diesel Injector Clean (ADF – Our best seller), Diesel All-In-One or Diesel Injector Clean + Cetane Boost. These additives also provide specific additional benefits designed to keep diesel engines operating at top performance. Some say they can hear the difference. Omaha is starting to discover the AMSOIL difference now! We are keeping more and more cases so buy your months supply. We keep loads in inventory.

Lubricity Test

The ASTM D6079 High Frequency Reciprocating Rig (HFRR) lubricity test simulates wear in high-shear conditions, measuring fuel lubricity by rubbing a steel ball on a plate in a bath of fuel and measuring the wear scar. Independent testing reveals Diesel Injector Clean provides superior fuel lubricity over untreated fuel and fuel treated with two-stroke oil.

  • Better lubricity
  • Clean fuel system
  • Avoid EPA violations

August 2019 amsoil dealer magazine

We have plenty of supply here in Sioux Falls. Stan Houston’s and at our Tea Exit location by Marlins.

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Diesel Fuel Injector Problems: An Easy Solution

Written by Charleen

Diesel Owners Need to be Fuel (Injector) Experts

Mark Nyholm|

It feels like forever ago, but it’s only been 13 years since the U.S. Environmental Protection Agency (EPA) mandated reduced sulfur content in diesel fuel, in 2006.

Boy, were people angry. They knew sulfur helped protect their fuel pump and injectors from failure. Change is scary, and the thought of replacing expensive components even more so.

Diesel fuel injector problems more pronounced today

Fast-forward to today. I rarely hear anyone talking about this. But the problem is even more prevalent now than it was then. Modern diesels demand even more from the fuel pump and injectors than before, increasing the potential for failure. So, why aren’t people still up in arms?

My hunch is they have accepted the new reality. Or, they just don’t know what they don’t know when they buy a new truck today.

Today’s ultra-low-sulfur diesel fuel (ULSD) provides significantly reduced lubricity – a critical property in controlling fuel-pump and injector wear.

ULSD provides insufficient lubricity

While diesel fuel has traditionally had high lubrication properties, the de-sulfurization process that’s used to strip the diesel fuel of the sulfur content to meet ULSD requirements also strips the fuel of some of its organic compounds responsible for lubrication.

The ASTM D975 diesel-fuel standard mandates a minimum lubricity level. However, the Engine Manufacturers Association (EMA) wants the standard to provide for increased lubricity. But, while the EMA claims there’s a problem, it doesn’t carry enough clout to change the specification.

Since 2006, ULSD has accounted for nearly all diesel available in North America. Why? Because the EPA mandated reduced sulfur to curb harmful emissions.

ULSD now contains a maximum of just 15 ppm sulfur, compared to fuel that had up to 5,000 ppm sulfur prior to EPA regulations.

Waxes in diesel fuel lubricate the fuel pump and injectors, helping fight wear. Without them, the highly engineered components in modern diesels, particularly high-pressure common-rail (HPCR) engines, can wear out and cost thousands in repairs.

Today’s highly engineered diesel fuel injectors can suffer from even minimal deposits.

Diesel injector deposits kill performance

They can also develop deposits that interfere with an optimum spray pattern, reducing power and fuel economy.

The editors of Diesel Power Magazine covered the ULSD problem in the April and May 2019 issues.

As reported, the Bosch CP4.2 fuel pump that comes stock on 2011-2016 Duramax engines has led to thousands of catastrophic failures. It has culminated in class-action lawsuits in Texas and California against Bosch, GM, Ford and other vehicle manufacturers on behalf of individual diesel owners whose vehicles use that pump.

Diesel fuel pump failure costs big bucks

When the CP4.2 fuel pump fails, it instantly contaminates the entire fuel system with metal particulates, costing $8,000 to $12,000 in repairs. The magazine reiterates what AMSOIL has been saying for years:

“The way to be proactive in protecting a CP4.2 equipped diesel from an early demise is being diligent about using fuel additives that add lubricity with every fill-up.”

Diesel Power Magazine

The CP4.2 pump is said to fail because of two reasons:

1) It’s designed with about 20 percent reduced flow volume than the previous generation pump, requiring it to work even harder.

2) ULSD isn’t providing enough lubricity.

 

Our testing of base fuels across the U.S. confirms the second point.

ASTM D975 requires diesel fuel to limit the wear scar in lubricity testing to 520 microns. The EMA, meanwhile, sets its own, stricter requirement of 460 microns.

As the chart shows, many of the fuels (blue bars) failed to limit wear to 520 microns. And none of them met the EMA’s 460-micron limit.

Diesel Fuel Additive lubricity Improvement

Fuel treated with AMSOIL Diesel All-In-One performed far better (red bars). It not only met the ASTM D975 standard, it also met stricter EMA lubricity requirement.

Buy AMSOIL Diesel All-in-One

You can find the same technology in AMSOIL Diesel Injector Clean and Diesel Injector Clean + Cetane Boost.

Buy AMSOIL Diesel Injector Clean

Buy AMSOIL Diesel Injector Clean + Cetane Boost

Our diesel additives deliver a healthy boost in lubricity to help lubricate diesel fuel pumps and injectors. The extra lubrication helps prevent wear in fuel pumps and injectors. They’re also great for maximum winter performance, too.

I strongly recommend that all diesel owners use AMSOIL diesel fuel additives with every tank of fuel.

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