Best Synthetic Motor Oils

Motor oil is the life force of the vehicle. Think of it like the blood that keeps it going. It is an absolute essential, and without it, your car would barely be able to leave your driveway or garage.

Whether you are a newbie driver who is looking for oil for the first time, or someone looking to make a switch from your long-used traditional oil for a synthetic alternative, you may well have heard lots of debate over whether synthetic is better than traditional, and then even more debate over what the best of the lot is.

Best Synthetic Motor Oils

All this debate can make the search for the best synthetic motor oil pretty confusing, especially when you consider the fact that actually, most of the higher quality synthetic oils out there perform pretty similarly.

To make your lives a little easier, and to prevent you from endlessly scrolling through the internet, we have decided to compile our Top Five choices for Best Synthetic Motor Oils, as well as give you a super informative Buyers’ Guide so you know exactly what we used to judge the oils.

The Buyers’ Guide will also help you to know exactly what you should look for when you are figuring out the best oil to buy for your vehicle. So buckle up and start your engines, because you are in for an information-packed ride!

Top 5 Best Synthetic Motor Oils


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AmazonBasics Full Synthetic Motor Oil


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Castrol Full Synthetic Motor Oil


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Valvoline Advanced Full Synthetic Motor Oil


AmazonBasics Full Synthetic Motor Oil

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First on our list is the raved-about Synthetic Motor Oil from AmazonBasics. Take our word for it, there is nothing basic about this oil.

It is available to buy in a variety of configurations (these are the viscosity ratings that are explored in more detail in our Buyers’ Guide) which means the oil will suit most vehicle engines.

As well as these configuration options, there is also the option to purchase oil suitable for high mileage cars. This is also a synthetic oil. This means it is great for those cars that have a higher mileage on them. The 75,000-mile marker and above will be ideal for this high-mileage oil.

As if all these choices weren’t enough, you can even select different size options, meaning you can stock up easily and not have to worry about running out of oil for ages.

The oil has a high-resistance to viscosity and thermal breakdown. As well as this it has compounds in the oil that can help prevent build-ups that cause rust and corrosion. It is formulated to ensure longer draining times.

This oil also features additives to reduce friction between parts of your motor that are constantly moving.

The last feature of this oil that should be discussed is that it can help reduce emissions from your exhaust, helping your vehicle to be as environmentally friendly as possible.


  • Additives to reduce build-ups that cause rust and corrosion
  • Lubricates your engine and reduces friction
  • Reduces emissions from your exhaust
  • Option to buy a high-mileage version
  • Multipacks for stocking up
  • Variety of viscosity ratings to suit most cars


  • There is no clear strip on the bottle to easily see how much you are pouring


Castrol Full Synthetic Motor Oil

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Next on our list, we have the Full Synthetic Motor Oil from the leading brand, Castrol.

Their synthetic motor oil has various options in terms of viscosity options. Of course, your needs will be dependent on your car’s needs. You need to check this before purchasing. You can also buy it in various bottle sizes and multipacks.

Castrol highlights the fact that most of the damage is done to your engine within the first 20 minutes or so of car usage on each journey. This is because oil drains away from critical parts of your engine when the engine is turned off, meaning it takes longer to fully cover the engine when it is turned on.

They say it is therefore vital that protection is offered from the start. This is why they have formulated an oil that is particularly good for reducing engine wear, as well as keeping all the essential parts of your engine adequately lubricated.

The protection this oil gives your engine is superior, due to the molecules that are in the makeup of the oil. They cling to all the critical parts of your engine to ensure that when the engine is off, the oil doesn’t drain.


  • Instant protection for your engine from the instant you startup
  • The oil clings to parts of your engine that critically needs protection
  • Available in various sizes and multipacks


  • Some users say that it doesn’t hold up well in harsh winter conditions and the oil thickens a little


Valvoline Advanced Full Synthetic Motor Oil

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Yet another oil that comes in a variety of viscosity configurations, making it suitable for a wide variety of vehicles. As always, don’t forget to check your particular engine requirements first.

This brand also comes with the option of buying oil that is specially formulated for Modern Engines, whilst still being Full Synthetic.

Perfect for you lucky things with a brand new car! It also comes in several sizes, as well as having the option to buy multipacks – ideal for stocking up or if you have numerous vehicles to care for.

This product offers supreme, high-quality protection from extreme temperatures. It can also help to protect from build-ups of sludge, ensuring cleanliness for your engine and all the intricate parts of it.

Valvoline has ensured that its formula contributes to reduced exhaust fume emissions, too. This makes it very helpful for those of you trying to be a little more environmentally friendly with your lives.

A desired feature in all oils is that it can flow fast. Due to the excellent viscosity of this one, it will flow and protect your whole engine from the very first moment you start it up.

It also features an easy to use pourer, ensuring you don’t waste a drop or end up with a minor oil spillage! This feature is only included in its 5-quart bottle version.

The brand has long been a leading name in the industry, and are fully American owned and manufactured, with production taking place in Ashland, Kentucky since 1920 –  All those years of experience have proved themselves with this product, that’s for sure, especially when considering the company themselves have been operating for over 150 years.


  • A company with over 150 years of experience
  • The easy pouring lid on there ensures safety when pouring and no waste
  • Reduces exhaust fumes
  • Additives to stop sludge build-up and blockages


  • Some customers noticed that this oil caused coloration changes on the oil cap of their vehicle and in the valves


Castrol Edge Full Synthetic Motor Oil

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Another Castrol product makes it onto our list! Their Advanced ‘Edge’ product truly does have the edge (excuse the pun) since it so completely protects your vehicle.

It has additives in its ingredients list that can help to deter build-ups in your engine from debris and sludge. They also decrease the formation of engine deposits which, in turn, helps to maximize your engine’s response time.

As if that wasn’t enough, it offers full protection for the engine drain time, meaning that even when the engine is just starting up, the oil has already clung to all the important parts of the engine keeping them lubricated and protected even in this crucial moment.

The drainage time is also far shorter with this product than others on the market, making it an excellent choice for shorter journeys as well as longer ones.

It comes in a range of sizes, and like others can also be bought in a multipack so you can stock up.


  • Helps to maximize your engine’s response time
  • Full protection from engine start-up
  • Extra additives to prevent sludge and debris from building up and causing blockages
  • Coats the crucial parts of your engine to ensure they are protected all the way through


  • Some users found that this oil didn’t last as long as some others on the market


Valvoline High Mileage MaxLife

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Last but certainly not least is yet another brand name that we have already seen, but this time it is a slightly different version of their Synthetic Oil.

This, their high mileage version with MaxLife Technology is ideal for those of us with older cars and older engines.

Do you have over 75,000 miles on the clock? If the answer is yes then this is the one for you. We go into a little more detail in the Buyers’ Guide about how mileage can affect your ideal motor oil choice (and vice versa), but suffice to say, if you do have a slightly older car, you need to give it a different level of care.

This is where Valvoline comes in. Their high mileage oil is formulated with a film that is both thick and durable, giving your engine that extra protection and to help to prevent it from breaking down.

This oil features additives in it that acts as a detergent to help cling to debris and sludge, preventing harmful blockages and build-ups. This is especially needed for those older cars that are more prone to this kind of damage.

The antioxidants that are added to it helps to prevent this too by stopping oil from breaking down quickly, in turn deterring sludge.

As with all the other choices so far, this product comes in a range of different configurations, meaning you can find the correct viscosity rating for your particular engine (please check with your manufacturer or car manual first!).

There are also a number of size options when buying this, as well as the option to place a bulk order with the multipacks they offer. The 5-quart size is the most popular because it comes with the added ease of use when pouring it, too.

No more oil spills in your garage!


  • The ideal choice for all cars with high-mileage on their clocks
  • Extra protective, lubricating all parts of the engine
  • Options to buy different sizes and multipacks
  • Easy pour lid


  • Some customers have found that this product leaks sometimes

Best Synthetic Motor Oils Buying Guide

To find the best synthetic motor oils, we have considered a range of features that we think all oils should include, ensuring the absolute best quality oil money can buy.

We think these are the factors that you should consider, too, when buying your synthetic motor oil.


One factor that should be considered when it comes to choosing a synthetic oil for your car is the mileage allowance in the oil, as well as the mileage of your own vehicle. For example, cars that have more miles on them, such as 75,000+ may benefit from an oil that is specially formulated for this reason.

Likewise, if you plan to drive your car long distances for longer periods of time, your oil needs to be up to scratch to be able to cope with the pressure on the engine.

You want the oil you choose to last and to last well, at that. It needs to perform well and do its job over a long period of time. Couple this long-lasting oil with a good oil filter and there you have a match made in heaven.

In terms of numbers, most synthetic motor oils on the market tend to last 7500 to 15,000 miles. In terms of time, they last around half a year to one year. It is a case of whatever limit is met first. That means that when looking for oil, you should not go for one that lasts less than 7500 miles.

Oil Viscosity Rating

Now for the science-y stuff (*throws on a white lab coat and glasses*)! This section is arguably the most important consideration that needs to be taken into account when shopping for new motor oil.

 This can get a little confusing so we are going to break it down for you. The texture of oils can be altered by temperature. When the oil is cold, it gets thicker. When the oil gets hot, it gets thinner.

Neither of these is particularly desirable for your car engine, as thick oil means that parts of your car engine, such as the fuel pump, have to work unnecessarily hard.

This can cause issues with the fuel pump, as well as causing issues with fuel economy as you will be using more gas. If the oil is too thin, there will not be enough lubrication between the moving parts of the engine.

What’s more is that every single car will have a different, and unique need for oil. The viscosity level needed for each car will differ, and it is an absolute necessity that you consult your car’s manual to find out the exact oil that you need because buying the wrong one will mean having oil with a viscosity that is possibly incompatible with your vehicle.

Each synthetic motor oil should have a viscosity rating clearly stated on the bottle. This rating is worked out based on a number of factors including, operating temperatures and external temperatures, as well as the engine load.  The measurement rating consists of two numbers:

  • The first number shows the level of viscosity when the temperature is freezing, meaning it is zero degrees Fahrenheit (0℉). This first number is then typically followed by a W, which simply means winter, signifying the colder temperatures.
  • The second number that is given refers to the level of viscosity when temperatures reach 212 degrees Fahrenheit (212℉) which is normal operating temperature.

The most common ratings for gasoline engines are 5W-30; 5W-20; and 0W-20. For diesel-powered engines, this is slightly different, and they are commonly 15W-40 and 5W-40.


Another relevant consideration to make is the addition of any additives in your synthetic motor oil. Additives get put into the oil to increase certain properties. For example, remember that viscosity we just talked about? Well, manufacturers can actually add in viscosity-index improvers to help with this.

There are a whole manner of things that can be added such as detergents and dispersants to help filter out any gunge and gunk, ensuring cleaner oil as well as stopping any build-ups and blockages.

They can add conditioners for oils specifically made for older engines too to help the smoother running of the car. Anti-wear agents are another popular additive as they can help reduce and prevent wear on the moving parts of your car engine.

Some of these additives certainly seem desirable, and you should make sure you think about any additives that are a must-have for your needs.

Other factors

Experts say that you can also look out for other factors that can affect your synthetic motor oil such as Pour Point and the Total Base Number, however, both of these factors tend not to even be listed on descriptors of oils when buying online.

Generally speaking, the higher the Total Base Number, the longer your oil will last. It is measured based on the capacity of the motor oil to neutralize acid generated by the engine. Pour Point refers to the lowest temperature at which oil can be poured from its canister and relates to viscosity.

As we say though, these can be difficult to determine online and it is generally the case that both of these conditions will be met anyway with all high-quality synthetic motor oils.

Final word

To conclude, we are sure you now know so much more about synthetic motor oil and that our handy Buyers’ Guide and top picks have helped you choose the perfect motor oil for your needs.

Safe driving!