Amsoil vs Royal Purple, the Comparison and Reviews

When you next go shopping for your car or truck engine's oil, which brand and product will you choose? Amsoil or Royal Purple. For now, let's take a detailed look at these two popular products and see which one makes the day.



Royal Purple


Not recommended


Drain Miles

25,000 miles/12 months

12,000 miles/12 months


Below 4000

Above 6000


Gear lubricant

Engine lubricant only


4qts+ Filter



Both brands, Amsoil and  Royal Purple are from reputable manufacturers in the market. Let's look deeper into main properties of these products to enlighten you.

AMSOIL VTWIN Synthetic Oil

If you are an occasional rider, you might be wondering what will happen to the motorcycle engine due to extended storage. Besides wear and tear, not riding the bike for long, coupled with humidity, can lead to corrosion that triggers roller bearing problems and loss of compression.

The Amsoil VTWIN synthetic motorcycle oil is manufactured to not only address the rust and corrosion problems but blended with special antirust additives. They offer the engine rust protection from acids while in storage, to enhance its performance and life.


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Ridding your motorcycle in extremely high temperatures is pretty cool with this product of  Amsoil. The oil is formulated with oxidation inhibitor additives to be thermally resistant under high-temperature. The additives also keep your engine clean and healthy by preventing sludge and carbon emissions in the worst conditions.

This product is equally effective in protecting primary chaincases and transmissions, such that you don't need to incur costs on additional lubricants. In fact, it has zero thinning and has no friction additives to perform as a gear lube without any problems.

AMISOIL 20w-50 synthetic oil facilitates smoother clutch shifting, reducing internal temperatures for a more extended engine and clutch lifespan.

Best features

  • Reduced carbon deposits longer use
  • Robust additive levels for engine cleanliness
  • Best 20w-50 motor oil for bikes
  • Compatibility with other motor oils
  • Pros

  • It offers two in one protection for transmissions and primary chaincases.
  • Its formulated with anti-corrosion additives for long-term bike storage.
  • Reduces friction for smoother clutch shifts and engagements
  • It can be added to existing oil without draining it.
  • Cons

  • Adding to other oils may reduce performance
  • Racing engines demand more frequent draining.

  • Royal Purple Synthetic Motor Oil

    Royal Purple is a brand name in the auto-care industry, releasing some of the best products, trusted, and reliable products. The high-performance synthetic motor oil is another great product of choice for most motorists.

    Is your current oil struggling to keep up with your engine speed, extreme temperatures, and load? Well, the Royal Purple's high-performance oil comes with a special additive known as Synerlec.

    This technology increases the oil's viscosity and strength to keep your engine performing at its best under all conditions and pressures. Also, you benefit by saving a few coins on fuel consumption per mileage.

    Royal Purple 12530

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    Above this, the oil is compatible with other conventional and blended oils, including other synthetic brands without negatively affecting the performance. And you don't have to drain the existing oil bit can add on it.

    It also features basic components that enhance engine protection against corrosive acids that cause wear and tear of engine parts. It's a product you should consider if your vehicle is a high performer and used for daily tasks.

    Irrespective of the condition of your engine, whether new or old, Royal Purple offers you a complete solution to keep your vehicle purring seductively.

    Best features

  • Has superior acidity protection
  • Incorporates the Synerlec technology for high performance
  • It's from a trusted and respected brand
  • Compatibility with other blended and synthetic oils
  • Pros

  • It is compatible with other conventional oils smooth switchover.
  • It offers engine protection from corrosion for longevity.
  • It performs exceptionally well under extreme temperatures.
  • It offers better fuel efficiency in both new and old vehicles.
  • It's a versatile product for both gasoline and diesel vehicles.
  • Cons

  • It has cost more than other products
  • Some users comment on no difference in performance.

  • AMSOIL vs Royal Purple Test Battle

    Which was the first oil change that you ever performed? How did you arrive at that choice? Was it preferred due to your mechanic's recommendation, or maybe your family used it ever since?

    There isn't any single methodology, scientific or otherwise, to determine which oil you should use. Every motorist will either believe in a brand, historical experience, peer influence, among others.Therefore, you should understand that any comparison needs to be handled with care due to personal opinion.

    However, let’s put the AMSOIL and Royal Purple brands on some head-on tests and see how they behave. After that, maybe we can both agree on some logical facts.

    To  arrive at a logical conclusion, we opt to use the third-party lab testing results. In this case, let's consider the American Culture of Testing and Materials (ASTM) to make a comparison.

    Click here to read an ultimate review of Synthetic Oil

    Four Ball Wear Test

    The test is the first test to differentiate the horses from the donkeys. This lab test is conducted by pressing and spinning a metal ball down between three different balls in a bath of oil being tested. The balls are arranged in a triangular pattern.

    Now, how do you determine the better oil? It's simple; the better one will secure the metal ball, resulting in smaller wear. That is, a smaller average scar diameter translates to a better oil performance in the test. In this test, the AMSOIL tends to have a smaller wear scar than the Royal Purple.

    However, the difference in wear between the two is marginal. But since we are talking about your engine's health, the slightest weaknesses may result in greater overall damage. Hence, AMSOIL wins the first round in this battle of performance.

    Also Read:

    Cold Cranking Viscosity Test

    Ever tried to start your car in winter, and it feels like the battery is running low! Usually, the engine is cold after a long period of idleness, or the outside temperatures are low. This affects the thickness and stickiness of engine oil. It can be traumatizing if you have an appointment, and the engine won't just kick.

    The best oil is, therefore, one that flows smoothly throughout, and in between the engine parts under low temperatures immediately, you ignite the engine. Both the AMSOIL and Royal Purple are synthetic oils which ideally are designed to offer superb performance under low temperature.

    The less time it takes for the oil to move from the pump to through your engine, the better it is. Surprisingly, though, the expected uniform performance of the two synthetic oils in this viscosity test suggests otherwise.

    After subjecting the Royal Purple and AMSOIL to the viscosity test simulator and at 30 degrees Celsius, the AMSOIL has a better cranking resistance than Royal Purple. This means your engine serviced with AMSOIL is more likely to start easily at extremely low temperatures compared to one with Royal Purple oil.

    You may want to know the factors that affect the oil change time

    NOACK Volatility Test

    Our third test is the NOACK volatility test, which determines the mass an oil loses when molecules vaporize through a process called volatilization. Like Royal Purple and AMSOIL brands, synthetic oils are a composition of important molecules that enhance engine performance.

    Some amount of these molecules may burn in the cylinders and evaporate at very high temperatures through crankcase ventilation. Hence, it results in a thicker and heavier oil that has a lower viscosity. When this happens, your automobile will exhibit increased fuel and oil consumption, wear and tear, and dark smoke.

    Our battling oil brands are heated to 150°C in carrying out this test over a specific time. The lighter molecules in both oils are expected to boil off, resulting in a loss of weight. This loss is expressed as a percentage of the oil that evaporates.

    The NOACK test demonstrates that AMSOIL has lower percentage loss than representing a higher resistance to volatilization under high-temperature service. Once again, this test makes the AMSOIL oil a better engine oil than Royal Purple.

    Hence, your guess is as good as mine; AMSOIL delivers better protection for your engine besides being cost-efficient.

    Thermo-Oxidation Engine Oil Simulation Test (TEOST)

    The other quality of engine oil you may ignore but is very important is the rate at which it deposits elements in various parts when it burns off. Under high temperatures, engine oils burn off and form deposits. These deposits may end up on your critical components, such as fuel injectors, turbos, and other areas.

    You can imagine what will happen when they block your fuel injector. If you don't, it will affect the injectors spray pattern leading to a reduction in combustion efficiency. Slowly by slowly, your engine loses its power.

    Now back to our two competing oils. Which one has a higher rate of deposits? This test reveals that the Royal Purple brand produces twice as much deposit as the AMSOIL oil. If you want an engine oil that doesn't burn off or if it does, the deposits are at their lowest, then AMSOIL is the better choice.

    Learn the tips on how to mix synthetic oil with regular oil.

    Total Base Number Test

    Our last test for the two brands is the Total Base Number (TBN) test. When your engine is running and the oil is being utilized, acidic components are produced. Such acids are harmful to your engine and will reduce their lifespan due to promoting corrosion.

    Besides, the rust will block the essential valves and vents, reducing engine performance. This test is simply the measure or the ability of an oil to maintain your engine clean and neutralize the acidic elements produce during the typical engine run.

    Both the AMSOIL vs. Royal Purple oils are manufactured with the basic components that reduces or should I say neutralizes the acid produced and its effects. The difference is in quantity and how the alkaline (basic) component is blended to manage the acid problem effectively. The TBN test determines which of the two takes the lead.

    A higher TBN value means more and better blending of the basic component to protect your engine. In comparison, this test reveals a much higher TBN value in AMSOIL oil than in the Royal Purple oil. Hence AMSOIL engine oil will guarantee you a longer lifespan for your engine than the Royal Purple oil.

    As seen from the independent lab tests, synthetic oils are not equivalent in composition and performance. From the standard tests, AMSOIL synthetic engine oil stands with a better score across all the parameters. It, therefore, proves to be a reliable brand for its value.


    The engine is the heart of every automobile, and engine oil is undoubtedly the blood that gives it life and makes it roar under all conditions. The best oil makes sure that your engine's parts are well lubricated to perform effectively.

    Hence, when one says your vehicle is well taken care of, it doesn't mean the body is flashy, but it's alive and purring. Engine oil prevents engine diseases, as curing it spare parts would be an expensive affair.

    We hope this review has given you more insight into synthetic engine oils and especially the AMSOIL and Royal Purple brands. While recommending each of the products under consideration, the AMSOIL oil had a better lab test score than the able competitor.

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