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7 Best Synthetic Oils – (Reviews & Buying Guide 2021)

Did you know that switching to synthetic motor oil you could lengthen the life of your engine? Not only that, but by choosing the best synthetic oil, you can boost fuel economy, extend the time between oil changes, and much more.
If you have made it to our review among the many synthetic motor oil reviews out there, then you probably are already considering switching. The problem is finding the best option out there that gives you the most for your money. Not only this, but it is crucial to find the ideal motor oil for your specific vehicle, the driving conditions, and overall use.
Don’t fret, we will guide you through the best options out there, the way to choose the ideal one, and present you with all the facts.

It’s easy to get lost among the numerous options out there. This is why our team has put together a list of the top 7 most trusted products to give you the comparison of the best synthetic motor oils out there. These are all 100% synthetic oil brands that we have handpicked for this list based on their ratings and demand. Here they are in no particular order:

Best Synthetic Motor Oil Reviews

1. Castrol 03063 GTX Magnatec Full Synthetic Motor Oil

Castrol 03063 GTX Magnatec Full Synthetic Motor OilThe Castrol 03063 GTX Magnatec 5W-30 Full Synthetic Motor Oil offers 6 times better wear protection than the competition. It is developed to support and protect your motor even in severe driving conditions such as extreme temperatures, short trips, and heavy traffic. Its unique blend includes intelligent molecules that cling to engine parts, protecting against sludge buildup and wear.
Tested in the industry Sequence IVA wear test this full synthetic motor oil has proven to maintain critical parts of the motor four times smoother. It offers a high level of viscosity breakdown protection and boosted fuel economy.
The intelligent molecules in the Castrol Synthetic Motor Oil don’t allow the oil to drain from the critical parts of the engine. Instead, they protect it when your engine needs it most, during startup. This provides added protection and keeps the engine running smoothly. It is recommended that you use Bosch oil filters with this full synthetic oil.


  • Intelligent molecules in the oil provide superior wear protection
  • Fuel economy based on US Industry Standards
  • Prevents sludge buildup and maintains the engine clean
  • Protects against viscosity breakdown for more extended time between oil changes


  • Doesn’t perform well in low temperatures
  • Bottle leaks during shipping making a mess and causing loss of product

2. Shell Rotella T6 Full Synthetic Diesel Motor Oil

Shell Rotella T6 Full Synthetic Diesel Motor OilThe 1-gallon 5W-40 Shell Rotella T6 Diesel Motor oil is an excellent choice if you work with heavy machinery, diesel pickup trucks, and other on or off-road engines that require API CH-4, CI-4, CI-4 Plus, CJ-4, and CK-4 diesel oil. It’s unique Triple Protection Plus formula combines a fully synthetic base oil and additive technology that protects against oil breakdowns, deposits, and wear.
It offers the ultimate fuel economy and extreme high and low-temperature protection. The low ash technology protects particulate filters and exhaust catalysts on low emission vehicles. This oil can be used to replace mineral and synthetic-based oils in applications for low temperatures.
This is a great inexpensive option for all diesel-powered vehicles such as classic cars, tractors and trailers, pickup trucks, and even motorcycles that allow for an SAE 5W-40 motor oil.


  • No anti-friction agents making it ideal for motorcycle use
  • 1.5% improved fuel economy
  • Up to 10,000 miles between oil changes – depending on the application and age of the vehicle


  • Bottles aren’t adequately sealed causing leaking when shipped

3. AmazonBasics Full Synthetic Motor Oil

AmazonBasics Full Synthetic Motor OilThis motor oil is claimed to protect even under the most severe conditions. The AmazonBasics Full Synthetic SAE 5W-30 oil offers longer drain intervals and a high-quality blend. It helps improve fuel economy all the while providing excellent friction protection.
It is specially formulated to reduce low-speed pre-ignition and is developed to exceed GM dexos1 Gen 2 specifications. The AmazonBasics motor oil also meets or exceeds the requirements of API SL, SM, SN, and SN PLUS, as well as ISAC GF-5 and GF-4.
Although it is sold and shipped by Amazon basics, Warren Oil manufactures it. Although it’s an off-brand oil, it holds up just as good as the top out there. So don’t get put off by the name.


  • 8,000 to 10,000 oil change intervals dependent on vehicle and use
  • Dexos1 and Gen 2 Approved
  • Reduces low-speed pre-ignition


  • No oil indicator on bottle telling you how much remains
  • Not certified by any European car manufacturers
  • Not recommended for turbocharged cars

4. Valvoline Full Synthetic Motor Oil

Valvoline Full Synthetic Motor OilAlthough slightly more expensive the Valvoline Full Synthetic 5W-20 Motor Oil is a great option. It has excellent varnish and sludge protecting keeping the engine clean. Through faster oil flow during startup, this oil provides added high and low-temperature protection. This makes it an excellent option for severe driving conditions.
This oil is 100% US-made and meets performance requirements for all supercharged and aspirated turbocharged cars in North America. By switching to this oil, you will see an improved mileage and overall a smoother ride.
Most have experienced up to 10,000 miles between oil changes, but it all depends on the way you drive the car and whether you are diving it in extreme weather. What’s most important is that it offers excellent protection and quality viscosity for your motor.


  • Made 100% in the USA
  • Up to 10,000 miles between oil changes
  • Improves fuel efficiency
  • Suitable for supercharged and aspirated turbocharged cars


  • Bottles leak during shipping due to caps not adequately sealed

5. Castrol Edge High Mileage Full Synthetic Motor Oil

Castrol Edge High Mileage Full Synthetic Motor OilYou may have heard the rumor that switching to a synthetic motor oil on an older vehicle may cause problems. Fortunately, there are great motor oils for high mileage vehicles, like the Castrol Edge High Mileage 10W-30 Motor Oil. Explicitly developed for engines with more than 75,000 miles, this motor oil is an ideal way to make the switch.
Boosting overall short and long-term performance, it will give life back to your high mileage engine. Its unique fluid titanium technology will increase oil film strength and aid in the reduction of film breakdown. The high mileage oil blend will reduce deposits, oil burn-off, and most importantly, leaks.
Generally, most users have seen excellent performance and may not require an oil change for 5,000 miles. Also, it offers improved fuel economy and is API certified. They recommend you use a Bosch oil filter with this oil.


  • Developed for high mileage vehicles
  • May improve fuel economy depending on the age of the motor
  • The unique formula reduces leaks, deposits, and burn off


  • The bottle is prone to leaking during shipping
  • May need an oil change as early as 3,000 – 5,000 miles if the motor has issues

6. Pennzoil Ultra Platinum Full Synthetic Motor Oil

Pennzoil Ultra Platinum Full Synthetic Motor OilThe 5W-30 Pennzoil Ultra Platinum Full Synthetic Motor Oil is a great option mainly because it is developed from natural gas, rather than crude. Its PurePlus Technology is designed to convert the natural gas into the ultimate full synthetic base oil. This means that there are fewer impurities than most base oils made from crude oil.
Unlike most other motor oils it is crystal clear. The unique performance additives that are combined with this quality base gives it it’s amber color. It offers complete engine protection that covers everything from water to extreme temperatures. The motor oil also flaunts high fuel economy, 65% cleaner pistons, and helps condition older seals.
It is developed to protect in extreme heat and prevent viscosity loss and thermal breakdown. Also, due to its faster low-temperature flow, it performs great in cold temperatures as well. The Pennzoil motor oil meets or exceeds ACEA AS/BS, A1/B1, ILSAC GF-5, API SN Plus, and API SN.


  • Can go up to 10,000 between oil changes
  • PurePlus Technology using natural gas instead of crude
  • Complete engine protection


  • Dexos1 Gen 1 certification not renewed and no dexos1 Gen 2 certification

7. Liqui Moly Premium Synthetic Motor Oil

Liqui Moly Premium Synthetic Motor OilThis last product on our list may be the most expensive, but you definitely get your money’s worth. The Liqui Moly Premium Synthetic Motor Oil offers the highest level of engine protection. It is SAE 5W-40 and is suitable for both gasoline and diesel vehicles.
It is an excellent option for low temperatures due to its rapid oil delivery. However, its high lubrication consistency makes it ideal for low temperatures. During a cold start, it offers instant lubrication, preventing rubbing and damage of the engine. Its unique formula is developed to protect your engine while keeping it squeaky clean.
Liqui Moly is manufactured in Germany and ideal for both gas and diesel cars. This is considered the best synthetic oil for European cars and exceeds all requirements of European car manufacturers. It is tested to be safe with turbochargers and catalytic converters.


  • Suitable for both gas and diesel engines
  • All-season performance
  • Up to 10,000-mile service interval
  • Safe with turbochargers and catalytic converters


  • More expensive than most

There is a wide range of full synthetic motor oils available, and finding the right one is crucial to maintaining your engine. There are many things to take into consideration, so continue reading our guide, and we will help you decide what product is ideal for your engine.

What Exactly is Synthetic Motor Oil?

This is the first step to choosing the ideal motor oil for your car. Although many people do not recommend the use of full synthetic motor oil for new vehicles, or changing to synthetic for high mileage vehicles, this isn’t always the case. The main is finding the one that is developed specifically for your engine.
Full synthetic motor oil is composed of base oil and additives combined with a carrier oil which helps the even distribution of said additives. Usually, the base oil is of the highest quality refined crude oil, or in some cases natural gas.
The oil is highly refined and comes in different grades. Group I and II are mineral oils that are extracted from crude. The higher quality is Group V, where the oil is compound based. The quality oil offers the necessary viscosity, but still requires additives for reducing engine sludge, increasing performance, and boosting mileage.

Synthetic Motor Oil Buying Guide

Best Synthetic OilDifferent things must be considered when choosing the ideal synthetic motor oil for your vehicle and needs. The very first step is to check the user manual of your car and follow the motor oil recommendations. This should give you a major boost in the right direction. Once you know what you are looking for, it’s time to choose among the many options out there.

Top Things to Consider when Buying Synthetic Motor Oil

Here are some points you need to take into account when choosing a motor oil:

  • Are there extreme temperatures where you are located? Some oils do better in extreme heat, while others perform better in the cold. There are great options available that cover both extremes, but for the most part, you may have to consider changing the oil when the seasons change.
  • Will you be driving long distance, stop and go traffic, every day, or the car stays in the garage most of the time? This is another critical point to consider before starting your search. Some oils cater specifically to different driving conditions.
  • What is the mileage of your vehicle? This is important because some oils are made for newer cars, while others are developed specifically for higher mileage vehicles.
  • Is your car a gasoline or diesel engine? Don’t overlook this point. Though some oils work with both, some oils are specific to engine types.

Once you have the answers to these questions, it’s time to choose a quality motor oil that fits your needs. Remember, every engine is different, and there is a motor oil out there explicitly made to match it.

When you are ready to start shopping consider synthetic motor oils that have the following features to get the highest quality:

  • Verified by the American Petroleum Institute (API) – look for the starburst symbol somewhere on the bottle. Although not 100% necessary, this does give a guarantee of quality.
  • Synthetic Blend or Full Synthetic – the former is more expensive and the better choice, but if you have a tight budget, a blend is still better than conventional oil. Also, keep in mind that some oils that are claimed to be full synthetic are usually nothing more than a synthetic blend. This is why it’s essential to read the information about the oil and check reviews carefully.
  • Choose the oil viscosity – this determines the thickness of the oil at different temperatures. The number before the W is the rating at winter temperatures. The lower the number, the thinner the motor oil is.

The number following the W is the rating of the oil at average temperatures of engine operation. The higher the number, the thicker the synthetic oil is. You can use your vehicles user manual to guide you.

  • Check for a high viscosity index – above V, anything lower than this it usually means that the base oil isn’t refined.
  • The oil is dexos1 Gen1 and dexos1 Gen 2 certified and meets or exceeds requirements of ILSAC. This also isn’t necessary, as many high-quality oils do not have this certification, but it’s recommended.

Above all, one of the most important things to consider once you have found an oil that fits the recommendations of your user manual is to read the reviews. There are other things to consider, such as whether you will be driving in extreme weather. Also, how much you’ll be driving. The reviews may reveal if it’s suitable for your car as well and not just the manual.
Remember one thing, the higher the quality, the more expensive the oil is. Sometimes it’s better to spend more money to save you money in the long run. There are less costly options, but usually, that means you won’t be getting all of the benefits of synthetic oil.

What are the Most Important Synthetic Motor Oil Features?

Synthetic Motor Oil ReviewsThere are many benefits of synthetic oil. One of the biggest is the extended life of your engine. Whether your car is relatively new, or you’ve had it for a while, using synthetic motor oil will help boost fuel efficiency and improve your overall driving experience.

Testing has confirmed that over 70% of engine wear happens during the first 20 minutes of warmup. What synthetic motor oil does is boosts viscosity thus reducing friction drastically. In addition to this, the engine gets very dirty, and a quality oil will help keep it clean of sludge and dirt, preventing damage.
Even though a highly refined synthetic oil on its own is better than conventional oil, the additives are what really sets it apart. Here are some of the most popular:

  • Viscosity – improves or reduces the tendency of the oil to thin when the temperature increases.
  • Detergents – keep the engine clean by preventing the formation of high-temperature corrosion, rust, and deposits.
  • Antiwear Agents – protect the surfaces of the engine as the lubricating film tends to break down over time.
  • Friction Modifiers – boosts fuel economy by reducing engine friction.
  • Pour-point depressants – prevents the buildup of wax particles that reduce flow by clotting.
  • Antioxidants – prevents the thickening of the oil.
  • Foam inhibitors – when the crankshaft whips through the oil it makes it foamy, reducing the viscosity of the oil. This additive helps prevent foam formation.
  • Rust/corrosion inhibitors – this one is pretty simple, protects from moisture and acids that can corrode and rust the engine.

Some of these additives can be added to conventional motor oil, but the base is what makes it all come together for the best results. You may see an improvement, but it could never be to the extent that you get when they are applied to a well-refined oil.

Fully Synthetic vs. Synthetic Blend

This is a critical question for many. Sometimes a blend may be all you need, but if you are willing to spend a bit more for full synthetic motor oil, it’s well worth it. The main thing to remember is that even if you choose the less expensive synthetic blend over full synthetic oil, it is still a better choice than conventional motor oil.
You may have noticed that synthetic motor oil has become the requirement for most new vehicles these days. This is mainly because manufacturers are now able to build cars that have tighter tolerances than years ago with conventional oil.
The main difference is that a synthetic blend combines synthetic-based stocks with conventional motor oil, so you aren’t getting a pure base. In the case of fully synthetic oil, you get a refined synthetic base stock combined with the sought after additives. There are fewer impurities, and you can expect it to last longer than both conventional oil and a synthetic blend oil before needing an oil change.

Benefits of Using Synthetic Oil

Whether you select a full synthetic or a synthetic blend, you will still see a significant difference over mineral oil, or traditional motor oil. The different additives give the oil various benefits, and it may have all of the below listed, more, or a combination of them. It all depends on what your engine needs.

  • At service temperature extremes the engine will have better low and high-temperature viscosity performance
  • Better stability
  • Lower evaporative loss
  • Improved resistance to oxidation, oil sludge problems, and thermal breakdown
  • Longer drain intervals – this doubles as an environmental benefit because you generate less used oil waste
  • Improved extreme weather starts because of better lubrication
  • Longer engine life
  • Less oil burn off because it protects from deposits formation
  • Prevents oil passageway clogging
  • Less drag on the engine so boosted horsepower and torque
  • Improved fuel economy

The benefits are endless as they continuously come up with new additives to further enhance engine performance. There are, however, some drawbacks. One is that synthetic motor oil tends to be more expensive than traditional oil. Although, over time, this is an excellent investment and pays off.
Another thing you may want to consider is if the engine is high mileage or is a new engine that is in its break-in period. Though many consider this a myth, it’s good to check with your manual and mechanic before switching. Synthetic oil may clean your engine too well, thus opening up clogged leaks of a high mileage engine.

Buying Synthetic Oil vs. Regular Oil

Although if you’ve read our review and buying guide so far, it shouldn’t be challenging to choose. Still, many people don’t see the full benefit of choosing synthetic. All in all, it’s always better than conventional oil.
Traditional, conventional, or more rightly put, mineral oil does provide adequate lubrication, but cannot compete with the purity of quality refined synthetic. It cannot offer the same level of protection and performance. They are generally less chemically stable because they haven’t been so finely processed. Conventional oils also tend to acidify and oxidize easier, thus break down quicker. This means that even though they are less expensive, you have to change the oil more often.
Engines on synthetic oils tend to perform nearly 50% better, all the while emitting fewer emissions. With increased engine protection comes better oil and fuel economy. And so, this results in longer intervals between oil changes. Synthetic oils also have a higher resistance to thickening, so there is less engine drag.
With better weather protection you get quicker engine start time regardless of extreme temperatures. In general, it will increase the longevity of your engine simply by keeping it clean and reducing friction.

So is it worth the money? For sure. You may be surprised by how much more you will have to spend on synthetic oil over a regular oil, but your engine will thank you for it. Plus, over time, you will actually save money.

Quick Synthetic Motor Oil FAQ

There are always questions when you are looking to do something different with your vehicle. Frequently we find ourselves questioning whether it is worth it. There is still the worry of whether this may harm our precious car as well. So let’s take a look at some of the most common questions we’ve found regarding synthetic motor oil.

  • Q. I haven’t been using synthetic motor oil, and would like to switch. Will this harm my vehicle?
    A. This is a common question as there are many myths about switching to synthetic motor oil. One of the reasons is that conventional motor oil tends to clog up your engine to such an extent that it blocks possible leaks that may have opened up over time. When you switch to synthetic motor oil, its powerful cleaning agents may clear out these clogs and open up the leaks. The thing to remember is that these leaks should not be present in the first place and must be fixed. You may want to consult with your trusted mechanic to see whether a synthetic blend may be a more suitable option.
  • Q. I read somewhere that it’s not recommended to use synthetic motor oil on a new engine. Is this true?
    A. Although it’s best to allow the engine to break-in before switching to synthetic motor oil, you may want to double-check your user manual. More and more car manufacturers nowadays are building vehicles to work primarily with synthetic oil due to its many benefits.
  • Q. Can I use a synthetic oil eve if my car doesn’t have a high-performance engine?
    A. Another common misconception is that synthetic oils are exclusively for high-performance engines. This is far from the truth. Perhaps long ago, this was the case. But today, it’s the oil of choice for anyone that truly appreciates their car and wants their engine to perform at its best. Just make sure that you purchase the right viscosity thickness to fit your cars needs.
  • Q. Can I go back to conventional oil?
    A. Many people worry about getting stuck with the expensive alternative, regardless of its numerous benefits. Fortunately, if at any point you feel that you cannot afford a synthetic oil, or want to switch back, it’s no problem.
  • Q. Can synthetic and conventional oil be mixed?
    A. Yes, many people do this for different reasons. Just make sure that both of the oils are suitable for mixing.
    These are just some of the many questions people tend to have about synthetic oils. If you feel we haven’t answered your question here, we’d love to hear from you and do our best to be of help.

Don’t forget to check out our roundup of the oil additive reviews

Wrap Up

Deciding to switch to the best synthetic oil is easy; the question is finding the right one. Unfortunately, with its vast popularity over the years, more products that are below the expected quality have flooded the market. Finding the ideal oil can be difficult.
We hope that our reviews of synthetic motor oils have been of help in pointing you in the right direction. The most important thing to remember is to read your vehicles user manual carefully and always double-check the bottle of the motor oil to make sure it perfectly matches the requirements of your engine.
For more reviews and buying guides like this visit the CarOutfitter Ultimate Guide to Car Maintenance, our professional research team has all the answers to all your car maintenance needs.
We look forward to hearing from you in the comments below! Thanks for reading and as always – stay put!