Signature Series Amsoil 15w 40 synthetic diesel oil Review


You naturally want the best protection for your vehicle, after spending so much on it. Well, this is achieved using the best products for its optimum maintenance, which includes the right motor oil like Signature Series Amsoil 15w 40 synthetic diesel oil. This is a top-grade synthetic diesel oil that offers excellent wear protection to your vehicle.

Best protection for your engine

It’s when your engine rings and cylinder liners wear out that the engine consumes more oil and reduces fuel economy and horsepower. This problem, however, is much-taken care of by Amsoil Full Synthetic Diesel oil 15W-40 as it offers six times more wear projection to give your engine the security and extra protection it needs.

Optimal viscosity control

As the 15W 40 is a combination of top-tier synthetic base oils, it’s naturally resistant to oxidation and thick, soot contamination. Together with boosted detergent additives, it ensures all soot particles in the engine remain independently suspended. This in turn helps in preventing the formation of large, wear-causing particles.

All this minimises viscosity increase while controlling soot-related wear. Besides, the lower volatility of the oil helps maintain the oil’s viscosity after high-temperature services for maximum engine efficiency and protection.

Works well at extreme temperatures

Unlike other oils, the Amsoil 15W 40 works better than conventional and other synthetic diesel oils at resisting thermal or heat breakdown. This is because the oil doesn’t contain wax like other traditional oils, which makes it so much easier for the oil to remain fluid in sub-zero temperatures. This, in turn, provides for easier starts, reduces wear and also improves the oil’s flow.

Reduced oil consumption

As Amsoil Signature Series has a low rate of volatility, it consumes less oil in operation, and less oil vapour passes into the combustion chamber. There is less oil consumption even during extended periods of extreme hot and heavy loads.

Reduced wear

It’s thanks to the latest wear control technology that the 15W-40 synthetic diesel oil outperforms the Detroit Diesel DD13 Engine Scoffing Test by 600%. This is a test that measures the oil’s ability at resisting ring and cylinder bore scuffing, which is all due to Amsoil’s 45 years of synthetic engine oil design excellence.

Reliable performance even in winter

With the Signature Series 15W-40’s outstanding cold pour-point of -40°C, this is oil you can depend on for continuous service and performance through the four seasons.


  • Boasts of strong resistance to oil volatility
  • Can be easily poured even at cold temperatures of -40°C
  • Designed to resist unnecessary engine deposit formation
  • Can easily withstand extended drain intervals
  • 600% better wear control than other synthetic diesel oils
  • Can be used and depended on throughout the year
  • Less oil consumption even during extreme heat and heavy load conditions


  • Offers twice the manufacturer’s oil change interval than recommended by the owner’s manual to a maximum of 24,000 km or one year
  • Compatible with all other conventional, semi-synthetic and synthetic diesel engine oil brands
  • Perfect for customers looking for the best protection in severe operating conditions
  • Provides extra protection for longer drain intervals
  • It’s possible to extend the drain interval with an oil analysis


  • Extended oil change intervals not advised when engine is heavily modified and in severe service applications
  • Have to follow the manufacturer’s oil change interval if the car runs on gasoline with more than 10% ethanol
  • While it’s safe to mix 15W-40 with other brands, it reduces the oil’s extended drain interval and performance capabilities
  • Not recommended for use with aftermarket oil additives


Considering all these aspects and features of the Signature Series Amsoil 15W-40 synthetic diesel oil, this seems to be oil worth trying out on your vehicle. It not only offers the best protection for your car’s engine, but also comes with an extended oil change interval.

With its optimal viscosity control, it’s even possible to use the oil in extreme winter conditions of -40°C. And last, but not least, the oil is compatible with other conventional, semi-synthetic and synthetic diesel oils.


Like anything else, there are also other competitors in the market, boasting of a being an excellent synthetic diesel oil. One of them offering competition to this oil is Shell Helix HX5. This is oil that both cleans and protects the engine and also helps in reducing the noise produced by the engine.

It has an active cleaning technology that helps prevent the accumulation of deposits in the oil so that your engine runs smoothly. It is thus much more efficient than conventional mineral oils as it also helps avoid oil deterioration till the next oil change. It also boasts of low oil consumption and evaporation.

Final verdict

Looking at all this, the Signature Series Amsoil 15W-40 synthetic diesel oil is perfect for your car if you are looking for an oil that protects your vehicle the best even in severe operating conditions. While it’s predominantly used in diesel vehicles, it is also usable in gasoline engines. However, it may not offer that long an oil change interval if used in cars that run on gasoline containing more than 10% of ethanol.

While its competitor, the Shell Helix HX5 15W-40 is also good oil that offers optimal protection to your car, the Signature Series oil comes in smaller bottles that are easier to carry and store. Besides, the Shell Helix does not offer the best protection for your vehicle, making you wonder if it’s actually worth the buy as its rather expensive for its 5-litre bottle.

And unlike other conventional oils, your Signature Series Amsoil oil works well at extreme temperatures and in heavy loads. It’s quickly poured even at freezing temperatures of -40°C which means it gives an easier and quicker start in cold winters. Considering all aspects, the Amsoil 15W-40 is indeed great oil for your vehicle. However, it’s always better to remain on the safer side and check your vehicle’s user manual to ensure this oil is indeed safe to use in your car.

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