🥇 Best Synthetic Motor Oil Comparison In 2021- Top Reviews For Buyers

100% synthetic oil brands

Synthetic motor oils essentially have a chemical composition that provide superior, better protection for an automotive engine than conventional oils.

Choosing a 100% synthetic oil over a conventional oil can a number of advantages ranging from increased fuel economy, better engine performance, lesser engine wear and tear resulting in an enhanced enhanced engine life. They even help your engine work better in extreme temperatures and also protect essential performance auto parts such as turbochargers.

Here in the guide below, we explore different aspects of a synthetic oil to consider before buying along with the top selling synthetic blend motor oil reviews.

Top 5 Best 100% Synthetic Oil Brands - A Quick Look-up

best synthetic motor oil comparison
  • Royal Purple SAE HPS Full Synthetic Oil
  • Dimensions : 4.2 x 1.8 x 8.8 Inches
  • Volume : 1 Quart (Case Of 6)
  • Item Weight : 2 Pounds
best motor oil for high mileage engines
  • Mobil 1 Extended Performance Synthetic Motor Oil
  • Dimensions : 9.6 x 9.2 x 7.6 Inches
  • Volume : 1 Quart (Pack Of 6)
  • Item Weight : 8.3 Pounds
synthetic oil comparison chart
  • Pennzoil Ultra Platinum Full Synthetic Oil
  • Dimensions : 9.4 x 9 x 7.9 Inches
  • Volume : 1 Quart (Case Of 6)
  • Item weight : 23.7 Pounds
what is the best synthetic oil
  • Castrol Edge Extended Performance Synthetic Oil
  • Dimensions : 12.4 x 8.3 x 4.7 Inches
  • Volume : 5 Quart
  • Item Weight : 21.4 Pounds
motor oil comparison
  • Rotella T6 Full Synthetic Heavy Duty Diesel Engine Oil
  • Dimensions : 12.6 x 12.2 x 9.6 Inches
  • Volume : 1 Gallon Jug Pack Of 3
  • Item Weight : 2 Pounds

5 Top Rated Synthetic Oil Reviewed

royal purple synthetic oil review


  • Increased Horsepower.

  • Maximum wear protection.

  • Zinc/Phosphorus Anti-wear additive.

  • Exceptional oxidation stability.

In my opinion Royal Purple is considered to be the best synthetic motor oil brand as it is recommended by several mechanics. It has Royal Purple’s proprietary Synerlec additive technology. This, along with the zinc/phosphorus anti-wear additive blend, pumps up its effects by a significant degree. The additives included further protect the engine against metal to metal contact, even when it is under stress.

In-Depth Analysis

  • The first feature I noticed about this oil is its wide range of available viscosities. You get 5W-20, 10W-40, 5W-30, 10W-30, and finally, 20W-50. This simply means that you will probably be able to use it in most sort of climates, whether they are warm or cold.

  • The high film strength acts as a coolant. It reduces the wear and heat of the engine. Not just that, it further extends the life of the engine as well.

  • The seal between the piston ring and cylinder wall is improved. This is what improves on the horsepower and torque. It helps with the fuel economy as well.

  • The oxidation stability is better in this as well. This means that this oil will last longer before forming any residues. It improves on the mileage, and it cuts down on emissions as well. The advanced full synthetic oil solvency helps with the deposits. This effectively improves fuel economy and the lifespan of the engine.

  • There is only one noticeable con in my opinion. And that is, the price of engine oil is higher than the average stuff. But then, considering that this is pure synthetic oil instead of a blend, it is justified as well.


  • Better efficiency.
  • Better High mileage oil.
  • Better engine life.
  • Better for the environment.
  • Pure top-rated Synthetic Oil.
  • Better fuel economy.


  • Not so affordable.

Final Verdict:

I would recommend that you buy this oil when your vehicle is out of manufacturer warranty. I noticed considerably high efficiency overall. It worked on all levels as it claims. The rate is a bit of a let-down. But on my part, I am willing to compromise on it for what this oil offers. It is specially meant for protecting the engine and expanding the life span. Honestly, consistently using this high-performance engine oil brand for the last two years, I can vouch for this claim. So if you haven’t tried it out by now, I would suggest that you give it a go.

mobil 1 synthetic oil review


  • Full Synthetic Oil Formula.

  • Excellent engine oil lubrication.

  • Good Engine Protection.

  • Longer Engine Life.

Mobil 1 Extended is also a top rated synthetic oil that comes second on my list. It refrains from sludge and deposit buildup. It helps to reduce the wear and tear and overheating of the engine which may further cause problem with spark plug resulting in problematic ignition. And that too under a variety of operating conditions.

In-Depth Analysis

  • The rest of it comes with this being pure quality synthetic oil. One of the major criteria of good car engine oil is the lubrication it offers. This oil does fulfill that as well.

  • Its combination of additives helps to protect the engine. And it serves as a barrier to oil breakdown. This protects the metal parts of the engine.

  • It provides the basics as well. That includes good oxidation stability. This increases the life of the oil. That means that it takes time to build up any deposits. Or as I mentioned, this formula is exceptional in that area. And it also helps it to function well even in warmer temperatures.

  • Besides, it serves well in cold climates too. It goes well with engine seals and improves the lifespan of the engine.

  • The major con I can find about this product is that the additives used are not properly stated. This way, I can’t figure out the exact mechanics of the product. It serves its purpose well. But I can’t be specific about it.


  • Prolonged oil life.
  • Refrains from deposit formation.
  • Controls oil breakdown.
  • Compatible with engine seals.
  • Good oxidation stability.
  • Works well in low temperatures.


  • Unknown additives used.

Final Verdict:

I won’t say that I do not like this oil because that is not true. It works as well as the Royal Purple oil. However, it does not offer anything extra. And the Royal Purple works in versatile temperatures. That said, you can give this one a try too if you want a change. I do use it on an alternate basis. And the lubrication it offers is smooth as well. That is a good perk of this oil.

Pennzoil Ultra Platinum Full Synthetic Blend Motor Oil


  • Formulated with PurePlus Technology.

  • Drives extra 550 miles.

  • Better viscosity level.

  • Protects in extreme heat.

We have found that Pennzoil is the best full synthetic oil available in the market. It is one of the most well-known brands when it comes to automotive engine oil. This particular oil is, in my opinion, the best synthetic oil that they have launched ever. It is just the thing I need when I am on a long road trip.

In-Depth Analysis

  • This PurePlus Technology incorporated in this full synthetic blend oil is what makes it unique from the other two. It helps the liquid maintain a low viscosity, especially at colder climates. This is particularly useful because oil with thick viscosity will demand greater stress from the engine while pumping the oil. This helps reduce the load to a great level. This is achieved by combing the synthetic base oils with high-level additives. Even this base synthetic oil is made by compressing the purely natural gas. This is vastly different from the usual crude oils that are used for base synthetic oil. In fact, it is 99.5% more refined.

  • And the main part is, along with a comfortable consistency at a colder climate, you get the same at warmer ones as well. This has been proved under oxidation tests using base synthetic oils from other groups.

  • The engine and the synthetic oil are both protected well at low and even high temperatures. Engine protection is a big issue when it comes to any best synthetic engine oil.

  • While using it, I did notice that the chance of oil evaporating from heated engine surfaces, especially piston rings, is a lot less as well. This is very useful as the oil is used to its full potential.

  • However, in spite of these precautions, there have been complaints from a couple of my friends regarding its longevity. So if you are not prepared to take the risk of changing the full synthetic oil a bit more frequently, this is probably not for you.


  • Consistent viscosity level at colder climates.
  • Stabilized oxidation.
  • The base oil is made from natural gas.
  • Less wastage of oil.
  • Oil is better protected in the engine.


  • May not last that long.

Final Verdict:

Other than the longevity issue, I did not experience any such problems regarding this oil. Nevertheless, this is very good at maintaining the proper viscosity, even at extreme temperatures. Its restrained oxidation helps with hot weather. And the PurePlus technology is good for colder ones. The main part was the absolute lack of crude oils. Even most synthetic oils are chemically treated crude oils. I liked the fact that this product deters entirely from them. So yes, I will suggest that if you live in a hill station, this oil is really good to use. So, you can give it a try.

Castrol Edge Extended Synthetic Diesel Engine Oil For Car


  • 15000 miles performance range.

  • Maintains viscosity under pressure.

  • Titanium FST Feature.

  • Engine protection.

This oil steals the show when it comes to pure performance synthetic oil for diesel engines. You can even use it with sports and commuter vehicles. In fact, that is what I listed this product. But you can use it for conventional vehicles as well.

In-Depth Analysis

  • Its primary and most significant feature has to be its mileage. 15000 miles is a huge distance. On the longer road trips, it is always tiresome to replace the oil every few miles. With this oil, I do not need to face any such issues.

  • Apart from that, it is built to handle large amounts of pressure overall. This is useful considering the mileage it is capable of packing. It won’t do to have the engine fail in the middle of it. But this is due to the titanium additives blended into the oil.

  • Thirdly, we have here the muscle to hold the viscosity stability and that too even under tremendous pressure from the engine. The Castrol engine oil won’t thicken due to extreme heat, and this would ensure minimum deposits and sludge.

  • On the downside, I noticed that this oil is a bit thick in structure. So even though the viscosity remains the same, it creates a similar effect. It doubles the pressure due to this texture, and this can cause a bit of a problem. It is not that noticeable. But it is there.


  • Heavy mileage.
  • Stable viscosity.
  • Minimum sludge.
  • Increases engine life span.
  • Can withstand pressure.


  • Thick oil texture.
  • Oil pressure can increase.

Final Verdict:

I wouldn’t have voluntarily tried this oil out had it not been recommended to me by my mechanic. And I don’t regret it. I took a five-day-long road trip, and it served me fabulously. However, as good as it is on mileage and all the factors surrounding it, it does lack a couple of points. I am not too sure about the emission level of this castrol oil. It does boost up the lifespan of the engine as well. If you are the owner of a sports vehicle, I would recommend you to give it a try.

what is the best synthetic motor oil


  • Full Synthetic.

  • Low-ash Additive technology.

  • Excellent low-temperature flow.

  • Exceeds diesel engine application.

Last, but not the least, in my collection of the best synthetic engine oils, comes the Shell Rotella oil. As the name suggests, this oil is particularly useful for vehicles powered by diesel, whether they be new or old. However, it is not limited to that, and you can use it for vehicles powered by other types of fuel as well. Let me tell you the specifications first.

In-Depth Analysis

  • To start off with, yes this too is completely synthetic oil. Pure synthetic oil produces better results as opposed to a blend. This means that the base oil is a synthetic blend and not a high-carbon petroleum product. This helps it adjust to the situation while you are driving. Further, the product guarantees durability and enhances engine protection. The car oil is mostly low-ash. This ensures a bit of extra mileage and helps to improve the functionality of the engine alongside with your car appearance.

  • Secondly, the additive used is low ash. Apart from that, the level of phosphorus and sulfur is low as well. That means that operating the car becomes smoother than before. Moreover, my favorite feature is that you don’t need to spend as much effort on the maintenance either. This further ensures a low emission level with reduced carbon content. So, if you, like me, look for oils that have reduced emission levels, I would suggest this one, purely on that basis. Besides, the additives ensure low deposit content and low accumulation of dirt or debris. The heat resistant anti-breakdown feature protects the engine itself.

  • It has a cold-start viscosity feature as well. You don’t need to worry about warming up your oil, even in the coldest of weathers. This can ensure a smooth engine start even at -30F. Actually, among all the mentioned oils, this is a unique feature. This ties up with the low-temperature flow that ensures that the long-lasting engine oil remains runny in all kinds of weather conditions, while in the expensive engine.

  • If you want the maximum benefit from this oil, I would recommend that you try it out on your diesel vehicle.

  • As a con, I would advise against using it for gear motors. The consistency is too runny to be used with that kind of motor.


  • Low Deposits.
  • Low carbon level.
  • Low phosphorus and sulfur.
  • Reliable in extremes of temperature.
  • Protects against oil breakdown.


  • Cannot be used in gear motors.

Final Verdict:

Even though I placed it last, this is my second favorite on this list. And that’s pure because of the larger number of unique features it offers. Very few oils work that well in -30F as this one does. I was impressed with the emission level, and the idea of a low additive content appealed to me because of its pro-environment features.That said, you can try it out if it suits your engine type. If not, I am sure other products would. But honestly, it is one the best synthetic engine oils that you can ever use.

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What To Look Out For in Best High Mileage Synthetic Oil?

Among all the available options that all claim to be the best high mileage synthetic oil, it can be grueling to decide what exactly your vehicle needs along with your car spare parts. Apart from the different varieties of full synthetic oils themselves, there are specific qualities you should look out for in the oil you choose. I will start with the varieties. You can purchase full synthetic oils or a synthetic blend.

  • Full synthetic oil, of course, as the name suggests, is of the purest kind. It is developed through a chemical processing of the essential crude oil against the distillation process used to mineral oils. These are more consistent in their molecular proportions and have more stable qualities.
  • Semi-synthetics on the other hand, again, are what they are phrased to be. They are made through blending mineral oil with 30% synthetic oil. These are significantly less expensive and yet serve almost the same purpose as the purer kinds.

Next, we come to the criteria that I think is required while choosing your oil.

  • The first one is viscosity or the consistency of the oil you choose. This is not that simple, because as I explained earlier, the original consistency may vary according to the climate you drive in. This is marked by XW-XX. ‘W’ stands for winter and the digits after ‘W’ indicates the lowest temperature till which the oil can retain its original flow before it begins to thicken.
  • Next, are additives. More additives mean better resistance to sludge formation, leaks and dirt accumulation in the engine itself. These come in several types. Detergents clean out the rust and debris. Anti-wear additives safeguard the metal surface. Foam inhibitors reduce foam formation and retain the oils lubricating properties. Friction modifiers lessen the friction and enhance the mileage. And finally, the viscosity index improves preserves the consistency of the oil in high temperatures.
  • The oil should further be capable of proper lubrication of the engine components. It should lower the fuel economy as well.

Benefits of Using Good Synthetic Motor Oil

As to why you should prefer to use synthetic engine oil, here it is.

  • Unlike conventional oils that thicken at a higher temperature, it is easier to pour in. And the reverse is true as well. Conventional oil develops a viscosity at lower temperatures that you won’t find in their full synthetic counterpart. This works not only when you pour in the oil but inside the engine as well.
  • Temperature fluctuations would not affect the engine oil at any major level. This is because, conventional oils, better termed as mineral oils, have wax in its composition that solidifies at lower temperatures. This element is not present in synthetic oils.
  • For higher temperatures, on the other hand, the latter is capable of resisting any oxidation and hence the lack of deposits. Not only does the lack of oxidation in synthetic oils make it resistant to extremes of temperature, but it also has a longer life in the engine as well.
  • It is slightly less prone to forming sludge, definitely beyond what a conventional oil can offer you. Moreover, as a whole, the molecules are less exposed to friction which leads to a cooler working temperature that is better for the health of the car’s engine.

Of course, synthetic oils aren’t the only type, and if it suits you better, you can try out something else as well. However, I found this to be the easiest variety for my car.

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What is so great about synthetic oil?

Motor oils possess additives and base oils. Whereas synthetic oil is more refined that helps to improve the performance of the engine. Moreover, it helps the engine to stay clean, maintain viscosity, and make it resistant from rust.

What is engine oil viscosity?

Engine oil viscosity actually refers to its thickness and is indicated as 5W30 or 10W40 etc. In different climatic conditions, the engine oil should flow at a uniform rate to lubricate it to essential components. So it is important to have proper viscosity that synthetic oil carries.

Why switch from regular to synthetic oil?

If you care about the engine of your vehicle, then you need to make a switch. This is because motor oil composes of base oils whereas synthetic oil possesses more uniform properties to keep your engine protected. Around 70% of modern cars use synthetic oil to maximize the engine’s performance.

Can I mix different synthetic oils together?

Yes! Any synthetic oil is compatible with mineral oils or semi-synthetic oils, so you can make a blend of them. However, it is worth noting that the mixing of synthetic oil with other oils could comprise its quality and it might reduce its performance.

What differentiates fully synthetic oil from a semi-synthetic motor oil?

Fully synthetic oil is made of 100% premium performance liquid and non-traditional fluid, whereas semi-synthetic oil is a blend of other oils with this high-quality fluid as compared.

The Final Note

As with any car product with lots of options, it is very important to know what you are signing up for before you buy. If you were confused, I hope that this review helped you in your quest for the best synthetic motor oil.

With so many options to splurge on, you can go all out and get the right product for your car. As to why you should regularly replace your engine oil, I can list a ton of reasons. The high mileage full synthetic oil does the job of life-giving fluid to your vehicle. It cools your engine, lubricates it and keeps it running at all levels. Fresh oil gets rid of the accumulated debris that overused oil turns into gradually. It reduces emissions, fuel consumption and enhances the life of your engine. So I would suggest that you take care of your car and alter your oil, filter or check car battery on a periodic basis. Car batteries are indispensable fixtures of any vehicle. However, many of us do often face problems when it comes to cranking our machine during winter months. Hence we need to spend some time and effort to understand more about the car battery for cold weather failing which we will have a problem cropping up almost each and every day. And at last use only a good engine oil for enhanced performance of your engine.