7 Best Synthetic Oils of 2021

by Joshua Thomas

Synthetic motor oils offer a lot of advantages when used in a car engine. From improved viscosity to the many other features that help to improve a car's engine life, lubricating your car's engine with the best synthetic oil is definitely a good idea.

Although some older vehicles may not gain much from synthetic oils, most modern vehicles from the year 2,000 on will definitely get a cleaner engine with less tear and wear, when they run on synthetic oil.

The issue with synthetic oils though is that there are so many of them in the market, including those that are not very good. But here we provide a list of top-rated synthetic oils plus a buying guide to help you know what to watch out for when making your choice.

Editors' Picks for Top Synthetic Oils of 2021
Editors' Picks for Top Synthetic Oils of 2021

7 Best Synthetic Oils – Review

Valvoline 813460 SynPower Synthetic Motor Oil

1. Valvoline 813460 (Best 0W20 Synthetic Oil)

  • Good high and low temperature tolerance
  • 50% more wear protection
  • Ideal for turbo and super-charged vehicles
  • Superior sludge/varnish protection
Castrol 03101 Edge Full-Synthetic Motor Oil

2. Castrol Edge 03101 (Best Brand)

  • Top brand synthetic oil
  • Advanced & super-strong formula
  • Reduces deposit formation
  • Cuts down metal to metal contact
Valvoline 782256 MaxLife Synthetic Motor Oil

3. Valvoline 782253 (Best 5W20 Synthetic Blend Oil)

  • High-quality synthetic blend oil
  • Extra detergents 
  • Anti-oxidants included
  • Extra wear protection
Castrol 03084

4. Castrol 03084 (Best Full Synthetic Oil for the Money)

  • Budget-friendly oil
  • Fluid titanium technology
  • Decreased engine deposit formation
  • Entire engine protection
Shell Rotella T6 Heavy-Duty Full Synthetic Oil

5. Shell Rotella T6 5W40 (Best for Diesel Engine)

  • Very ideal for diesel engines
  • Improves fuel economy
  • Emissions system compatibility
  • High heat breakdown resistance 
Royal Purple 51530 5W-30 Synthetic Oil

6. Royal Purple 51530 (Best 5W30 Synthetic Oil)

  • Improved compatibilty
  • Good protection for catalytic emission system 
  • Superior corrosion protection
  • Better fuel efficiency
Mobile 1 120769 5W-30 High Mileage Synthetic Engine Oil

7. Mobil 1 120769 (Best for High Mileage)

  • Great oil for high-mileage engines
  • Includes seal conditioner for reducing leaks
  • Protects critical engine parts
  • Cuts sludge and deposits

1. Valvoline 813460 – Best 0W20 Synthetic Oil

Valvoline 813460 SynPower Synthetic Motor Oil
Valvoline 813460 SynPower Synthetic Motor Oil
  • Type: Full synthetic
  • Viscosity: 0W-20

When you demand the best performance from your car's engine, you'll also need to make sure that it gets only the best. And if it calls for the 0W-20 oil, the Valvoline 813460 is our best option for you.

Besides being the best 0W-20 synthetic oil in this review, this oil also features sludge protection, high and low-temperature protection, better fuel efficiency, and you can either get this 5-quart container or just a quart container, or  a 3-pack of 5-quart containers.

It's a premium quality and full synthetic oil, designed for high-performance engines and to fulfill the standards of all leading engine makers.

This oil will work on a variety of cars, including those that run on gasoline and on diesel. It's, however, not the perfect motor oil for high-mileage and heavy-duty diesel engines.

It also works well on hybrids and is the perfect oil for in-warranty services, where API specifications are strictly observed, such as with Toyota and Honda vehicles.

For high mileage vehicles and heavy diesel engines, this is not the best oil. But for any other vehicle it should do a fantastic job.


  • Wide temperature tolerance
  • Greater wear protection
  • Effective varnish and sludge protection
  • Helps to improve your car's fuel efficiency
  • Meets the performance requirements of most passenger cars


  • Not good for heavy diesel engines
  • Not recommended for high-mileage cars

2. Castrol Edge 03101 – Best Synthetic Oil Brand

Castrol 03101 Edge Full-Synthetic Motor Oil
Castrol 03101 Edge Full-Synthetic Motor Oil
  • Type: Full Synthetic
  • Viscosity: 0W-40

Castrol is one of those brands that you will never go wrong when it comes to motor oil and other lubricants as they are one of the global industry leaders.

This top brand presents one of its most advanced engine oil formula here with the full synthetic Edge 03101. It is a premium motor oil for the best engines with high-performance expectations.

This oil comes recommended by many leading car manufacturers, and it also meets the oil specifications of the largest carmakers in the world, including Ford's WSS-M2C937-A specification and BMW's LL-01.

Castrol guarantees that this oil is Titanium strong in reducing metal to metal contact. Additionally, this oil protects your engine under extreme pressure condition.

And besides this 0W-40 viscosity oil, you can also get this Castrol oil in the 0W-20 viscosity, which gives you more options for different vehicles and driving conditions.


  • Superior performance in extreme situations
  • Minimizes engine deposit formation
  • Reduces metal to metal contact
  • Meets the motor oil specifications of major car manufacturers


  • It's not cheap 

3. Valvoline 782253 – Best 5W20 Synthetic Blend Oil

Valvoline 782256 MaxLife Synthetic Motor Oil
Valvoline 782256 MaxLife Synthetic Motor Oil
  • Type: Synthetic blend
  • Viscosity: 5W-20

Older engines have different oil needs than newer engines. So, while other oils might offer you the best performance you can get, this high mileage Valvoline synthetic blend oil is specifically designed to meet the needs of older engines.

This oil packs extra detergents to increase the cleaning action of your engine. It also comes with seal conditioners to rejuvenate old engine seals and help protect them from leaking.

You should note that this oil formula is not ideal for all engines. Your car would need to have clocked 75,000 miles at least before it can truly benefit from it.

In addition to extra detergents and seal conditioners, the oil also includes antioxidants and extra wear protection to cut down on future engine wear.

For high performance engines, this oil might not be up to the task, but you can be sure that it will still not damage them and will offer decent lubrication.


  • Great for engines that have accumulated lots of miles
  • Superior wear protection
  • Keeps older engines clean
  • Prevents sludge and deposit buildup


  • Not designed for high performance engines

4. Castrol 03084 – Best Full Synthetic Oil for the Money

Castrol 03084
Castrol 03084
  • Type: Full synthetic
  • Viscosity: 5W-30

Although the service and performance that the oil delivers is always the most important factor, cost also matters. And if you are looking for an effective but more budget-friendly synthetic oil, the Castrol 03084 is a perfect choice.

This full synthetic oil uses fluid titanium technology to ensure it delivers a powerful performance under pressure. Also, it is formulated to minimize metal on metal contact, and to offer full engine protection to lengthen the vehicle's service life significantly.

With this oil in your engine, you are also guaranteed of minimal engine deposit, and it will also allow for relatively longer oil change interval, and hence saving you even more money.

While this oil does not seem to improve the mileage significantly, it makes up for this by giving the engine superior protection for its price.

Castrol also offers this full synthetic oil in other viscosity options, which includes the 5W-20 and 5W-40.


  • Relatively more affordable
  • Stronger performance under pressure
  • Protects the entire engine
  • Decreases formation of deposits
  • Reduces metal to metal contact


  • No significant MPG increase

5. Shell Rotella T6 5W40 – Best Synthetic Oil for Diesel Engine

Shell Rotella T6 Heavy-Duty Full Synthetic Oil
Shell Rotella T6 Heavy-Duty Full Synthetic Oil
  • Type: Full Synthetic
  • Viscosity: 5W-40

This Shell Rotella T6 formula offers lots of advantages over other engine oils. And it is specifically-formulated for the diesel engines. 

Its low winter viscosity of 5W makes it very helpful in cold weather by improving engine startups and improving fuel economy up to 1.5% while maintaining enough viscosity to prevent wear and tear.

Another important feature is its low-ash technology. This helps in reducing the poisoning or blocking of devices that treat exhaust gases for emission control, such as the catalytic converter.

In addition to keeping good emission levels, the Shell Rotella T6 also features improved heat resistance, as well as advanced additive technology for protection against deposits, wear, and oil breakdown.

This oil seems to thin a little too easily when compared to others, but you can easily avoid wastage by ordering just what you need to use at a go.


  • Works great on diesel engines
  • Helps with up to 1.5% better fuel economy
  • Improved resistance against heat breakdown
  • Offers an improved wear performance
  • Lower emissions


  • Gets thin quickly

6. Royal Purple 51530 – Best 5W30 Synthetic Oil

Royal Purple 51530 5W-30 Synthetic Oil
Royal Purple 51530 5W-30 Synthetic Oil
  • Type: Synthetic blend
  • Viscosity: 5W-30

The Royal Purple 51530 is a 5W-30 oil made from combining standard mineral oils with additives to give it an improved performance over ordinary mineral oils. 

These improved features include protection from corrosion, protection of the car's emission control system, better protection from wear, and an improved fuel efficiency as a result of the improvement in lubrication.

This oil will provide better protection for the expensive catalytic emission system. And this synthetic blend oil will also offer improved compatibility with fuels that have ethanol.

This oil meets the Dexos1 and ILSAC GF-5 performance standards, although it's rather too costly for a synthetic blend package.

For a synthetic blend oil, this product is relatively pricier but the performance you get makes it worth every buck.


  • Offers improved wear protection than mineral oils
  • Easily compatible with ethanol-containing fuels
  • Contribute to overall longer engine life
  • Improved fuel efficiency from less friction


  • Price is a bit high for a synthetic blend oil

7. Mobil 1 120769 – Best High Mileage Synthetic Oil

Mobile 1 120769 5W-30 High Mileage Synthetic Engine Oil
Mobile 1 120769 5W-30 High Mileage Synthetic Engine Oil
  • Type: Full synthetic
  • Viscosity: 5W-30

High mileage oils are the best engine oils for vehicles that have crossed the 75,000 miles mark. The engines are different from those of other vehicles, so they need special care as well.

This Mobil High Mileage oil is specifically designed to cater for the needs of such high mileage vehicles by focusing on better wear protection and an increased level of seal conditioner to protect the engine's seals and prevent leaks.

It also offers your engine a high level of sludge reduction, although you must change the oil in brief intervals until the sludge is cleaned out or decimated.

In addition to all its extra features for high mileage engines, this oil also carries out its primary duty of lubricating and protecting the engine.

Downsides are that it's neither ideal for new cars nor for high-performance engines.


  • Outperforms most standard high-mileage oils
  • Offers a quality overall lubrication and protection
  • Helps in reducing sludge and keeping the engine clean
  • Included seal conditioner helps to cut leaks


  • Not ideal for new cars
  • Not for high-performance engines

How to Buy the Best Synthetic Oil

The Best Synthetic Oil Buying Guide
The Best Synthetic Oil Buying Guide

1. Full Synthetic vs Synthetic Blend Oil

Full Synthetic

A fully synthetic oil is entirely made from synthetic materials while a synthetic blend oil is a mixture of a fully synthetic oil with standard motor oil.

Full synthetic oils like the Mag 1 20139 are custom designed to offer specific characteristics that a car needs for the optimal functioning of its engine. And for this reason, they were originally used mostly in high-performance cars. Their disadvantage is that they are costlier.

Synthetic Blends

Synthetic blend oils, on the other hand, combine the good features of fully synthetic oils with the advantage of standard motor oils, which is why a cheaper price.

And while they might not offer the same quality and long change intervals like the full synthetic oils, the synthetic blends like Valvoline 782253 will be very good for older engines.

2. Compatibility with Existing Oil

If you're upgrading from standard motor oil to synthetic oil and you're wondering if you can combine the two, the simple answer will be: Yes, you can but should you?

Nothing stops you from mixing both oils but remember that the major reason you're switching to synthetic oil is the many benefits it offers. So, mixing it with standard motor oil will naturally cut down on these benefits.

To get the best performance, you'll need to drain the oil before introducing the new one. Also, check to make sure that your vehicle is a modern engine (from 2,000 model) that will benefit from synthetic motor oil before going ahead.

3. Viscosity Grade

Oil viscosity is a measure of how thick or thin it is, and since oil tends to thin out at higher temperatures, heavier-duty engines need thicker or more viscous oils to keep running smoothly and prevent tear and wear when doing serious work.

On the other hand, if the oil is too thick, then your engine could suffer from startup issues. So, you need to use an oil with the right viscosity for your car's engine and this rating is usually provided in the car's manual.

If you haul heavy loads or drive a lot in a hot environment, then you can choose an oil with a slightly higher viscosity and if you live in a cold region or just use the car for light errands, then an oil with a slightly lower viscosity rating would be great.

Oil grades are either given as 5W-30 or SAE 30, for example. When a 'W' is present, it states the oil's viscosity at a cold (Winter) temperature, which in this case would be 5. The 30 though, refers to the oil's viscosity at 100 Centigrades, which is generally considered a standard engine-operation temperature.

4. Additives in the Oil

Additives are what make the best synthetic oils to stand out. There are so many types of additives that you'll find in a synthetic oil and different manufacturers also have their own unique formulas for combining these additives.

Here is a list of some common additives and what they are good for.

  • Anti-foaming agents prevent the oil from foaming
  • Anti-wear agents are different materials that lengthen an engine's lifespan
  • Antioxidants help prolong the oil's life by slowing down its degradation
  • Conditioners soften seals and help them to expand and contract better
  • Detergents help to clean up an engine and prevent the buildup of gunk and debris
  • Corrosion inhibitors protect your engine from corrosion
  • Dispersants stop the clumping of particles and the buildup of sludge

When to Change Your Car's Engine Oil

When To Change Your Car's Engine Oil
When To Change Your Car's Engine Oil

The old advice goes you should change your car's engine oil every three months or 3,000 miles but that advice has gotten outdated because of the many advancements in the automobile industry.

You can find many cars that can drive for up to 5,000 and even 10,000 miles before needing an oil change. This is thanks to improved engine design and manufacturer's requirements of using better-quality oils in modern cars.

To know the best time to change your car's oil, you'll need to conduct the owner's manual and then consider your personal driving habits. If you drive more intensely or pull heavy loads, then changing your oil before the recommended time isn't bad at all.

Else, you can just wait for the oil replacement light on your dashboard to come on. This is mostly possible in modern cars, of course, but you can also depend on the old oil level check as well.

You should check your car's oil level at least once a month. When the oil loses its transparency and turns really black, then it's time to consider changing it. You can also touch it and rub the oil between two fingers. If the oil feels coarse or gritty, then it probably needs changing.

A final condition to changing your car's oil is when you hear increased engine noise or you've simply clocked over 10,000 miles since your last oil change.


In making your choice of the best synthetic oil for your vehicle, you should focus on your engine and try to figure out which will keep in the best shape and deliver a superior performance.

From out recommendations, the Valvoline 813460 is our top option as it works great at both high and low temperatures.

But, for the motorists that prefer to save a few bucks on their oil but still get a top quality full synthetic oil, the Castrol 03084 is perfect.


  1. 5 Things to Know about Oil Changes for Your Car - Consumer Reports
  2. The Dirty Truth about How Often You Need Your Oil Changed - HowStuffWorks

About Joshua Thomas

Joshua Thomas just simply loves cars and willing to work on them whenever there's chance... sometimes for free.

He started CarCareTotal back in 2017 from the advices of total strangers who witnessed his amazing skills in car repairs here and there.

His goal with this creation is to help car owners better learn how to maintain and repair their cars; as such, the site would cover alot of areas: troubleshooting, product recommendations, tips & tricks.

Joshua received Bachelor of Science in Mechanical Engineering at San Diego State University.

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