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Designed with precision and backed by years of innovation, the AMSOIL Signature Series Max-Duty 15W-40 is more than just an engine oil - it's a commitment to superior vehicle performance. This AMSOIL Diesel Oil product is meticulously engineered to offer advanced protection under extreme pressure and high-temperature conditions, ensuring your engine remains clean, efficient, and robust for an extended period up to 600 hours, 60,000 miles or 1 year, whichever comes first.

This AMSOIL 15W40 unique formulation stems from premium base oils and high-performance additives, delivering excellent oil viscosity stability and reducing engine wear even in the harshest environments. This results in increased fuel efficiency and a substantial decrease in emissions, supporting your drive towards a more sustainable future.

The product doesn't just protect your engine; it enhances it. By resisting thermal breakdown and oxidation, it maintains its protective properties for longer, reducing the need for frequent oil changes and helps with compression ignition. Whether you own a heavy-duty truck, a race car, or a daily commuter truck, this synthetic engine oil is a singular solution for the exceptional care of your vehicle. Trust in the excellence of this AMSOIL 15W40, a signature of quality and unmatched performance. Competitively priced with Rotella 15W-40, Mobil Delvac 15W-40 and Valvoline Premium Blue 15W-40, amongst others. Order this oil and  DIY or take it to a one stop quick lube to have it installed for your next diesel oil change service! Become an AMSOIL Preferred Customer and get up to 25% off on your order!


Key points to keep in mind are:

  • Provides exceptional extreme-pressure protection.

  • Offers 6 times more wear protection (1 )than the competition.

  • Preserves the correct viscosity (thickness) of the oil.

  • Reduces oil consumption to a minimum.

  • Maximizes fuel efficiency for cost savings.

  • Performs exceptionally well in extreme temperatures.

  • Allows for confident extension of oil drain intervals.

    • (Note 1) Wear protection data is derived from third-party testing in the Detroit Diesel DD13 Scuffing Test for specification DFS 93K222 using 5W-30 as the worst-case representation.



The world of motor vehicles is driven by a series of mechanical and chemical interactions that collectively determine the performance of your ride. For all vehicle enthusiasts, fleet managers, and daily commuters, the longevity and overall health of their vehicle's engine is paramount. The lifeblood that keeps these engines performing at their peak is engine oil. One product stands out for its exceptional performance in this field - the AMSOIL Signature Series Max-Duty 15W40 Diesel Oil. A favorite of many fleet mechanics!

Engine Protection: The Lifeline of Your Vehicle

The primary role of any engine oil is to provide unparalleled engine protection. The superior engine protection offered by this synthetic motor oil is the result of its meticulously engineered formulation. With the ability to work under extreme pressure and high-temperature conditions, this diesel oil ensures your engine remains clean, efficient, and robust for extended periods. The formulation has a unique blend of high-performance additives and premium base oils that combat the adverse effects of heat and friction generated in the engine, resulting in less wear and tear on engine components and longer engine life.

AMSOIL Diesel Liner Test Result

Wear Protection: Adding Years to Your Engine

Reducing wear is another critical role for engine oil. The product's innovative formulation targets all areas susceptible to wear, offering a shield of protection that increases engine life. Even under intense workloads and high-torque situations, this synthetic engine oil has shown to resist break-down, thus maintaining a continuous protective layer on the engine components.

Keeping Turbos Clean: Boosting Efficiency

Modern engines, especially those fitted with turbochargers, demand a lot from engine oils. A critical requirement is keeping turbos clean. This AMSOIL Diesel Oil product, full synthetic diesel oil, excels at this, providing a solution that helps maintain turbocharger efficiency. It keeps them clean by preventing the buildup of deposits and resisting heat-induced breakdown that can harm other engine oils. Clean turbos equate to better performance and longer turbo life.

Rust Protection: Shielding from the Hidden Enemy

Rust is an often overlooked yet potent enemy for engines. Water, a by-product of combustion, and other contaminants can lead to rusting of engine components. This high-grade oil counters rust effectively, providing a level of rust protection that can keep the engine components free from corrosive damage. Its anti-corrosion additives form a protective layer on the engine parts, helping to keep the rust at bay.

AMSOIL Diesel Rust Test Result Graph

Maintaining Viscosity: The Key to Continuous Protection

The consistency of an oil plays a significant role in its protective capability. This product's viscosity control formulation ensures it maintains its thickness under varying conditions, providing an optimal level of protection throughout its life. It resists thermal breakdown, retains its protective properties for longer, and remains stable under different operating conditions.

Reducing Oil Consumption: Promoting Efficiency and Sustainability

With growing awareness about resource conservation, it becomes imperative that an engine oil does its part in reducing oil consumption. By maintaining its viscosity and offering excellent oxidative stability, this AMSOIL 15W40 diesel oil minimizes the rate of oil consumption. Its high-quality additives prevent unnecessary oil breakdown, which can lead to increased oil consumption. Hence, it not only helps the environment but also proves cost-effective for users by reducing the frequency of top-ups and oil changes.

AMSOIL Diesel Oil Consumption Test

Excellent in Cold and Hot Temperatures: All-Weather Companion

Lastly, but significantly, this 100% synthetic diesel engine oil demonstrates exceptional performance in both cold and hot temperatures. Its cold-temperature properties ensure easy start-up and quick circulation of the oil in freezing conditions, offering immediate protection. In hot temperatures, it doesn't thin out excessively or break down; it continues to provide robust protection, making it an excellent choice for a wide range of climatic conditions. Considered by many as the best synthetic motor oil on the market for diesel engines!


In conclusion, the AMSOIL Signature Series Max-Duty 15W40 is more than an engine oil. It's a comprehensive solution for superior engine performance, wear protection, turbo cleanliness, rust prevention, viscosity maintenance, oil consumption reduction, and weather versatility. This AMSOIL Diesel Oil product is the culmination of extensive research, innovative formulation, and a dedication to providing the best engine oil to the market. Whether you're a heavy-duty truck driver, high-performance enthusiast, or a daily commuter using a diesel pickup, this product offers a singular solution for exceptional vehicle care and unmatched engine performance. This product is competitive with other products such as Shell Rotella T6 15W40, Chevron Delo 15W40 and others in this league. Trust in the excellence of this 100% synthetic 15W40 premium product, a testament to the exceptional quality that AMSOIL represents. Order this product today and DIY or take it to a diesel oil change near me location, like a 5 oil change facility, Valvoline oil changes installer, another oil change services facility or your own motor mechanic to ensure professional installation. 






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