Car fluids

The 8 Best Synthetic Oils — Review and Buyer’s Guide

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Synthetic oils have very much stamped their authority as the most efficient and desirable type of motor oil on the market. From the mid 20th century until now, synthetic oils have grown and developed to give your car the best performance possible. 

Technical Terms

You might see some technical phrases thrown around (such as 0W-50), and if you’re familiar with synthetic oils already, you can skip right ahead. However, if you might get confused down the line about what “drain interval” means or what “0W-50” describes, here’s a quick overview.

Firstly, drain interval is a fancy way of saying “the time between oil changes”. It is imperative to change your oil frequently enough to prevent buildup of residue or a slowing down in your engine’s power. 

So, if a product is offering a recommended drain interval of 10,000 miles, it can be assumed that it offers a more wear-resistant product than one with, say, 5,000 miles. 

As for the descriptions like “10W-50”, they describe the viscosity (i.e. thickness) of the oil in question. Specifically, the “10W” part denotes the maximum viscosity of the oil in conditions of low temperature (where the W stands for winter). On the other hand, the “50” on the end suggests the viscosity of your oil for 100°C, meaning that an oil that is “5W-40” would always be thinner than our “10W-50” example. You should pay close attention to this figure, as your vehicle only takes a certain range of oil viscosities. 

Short Overview

Now that you’re a bit more familiar with synthetic oils (if you weren’t already), let’s take a look at the best ones on the market and what separates them. Generally, they aim to accomplish the same task; however, some do it better than others, which we will explore below.

ProductPriceAmountRecommended Drain Interval (mi)ViscosityLink
AmazonBasics High Mileage Oil$5 quarts5,000-6,0005W-30Check price
Castrol 03087 Extended Performance$5 quarts20,0005W-30Check price
Shell Rotella T6 Full Synthetic$$1 gallon5,000-6,0005W-40Check price
Castrol 03057 GTX Magnatec$5 quarts3,000-5,0005W-30Check price
Mobil 1 120760 0W-40 Synthetic Oil$$5 quarts5,000-10,0000W-40Check price
Valvoline Advanced Full Synthetic SAE 5W-20$5 quarts5,0005W-20Check price
Mobil 1 106035 5W-50 Full Synthetic (Pack of 6)$$$
6 quarts5,000 – 10,0005W-50Check price
Pennzoil Ultra Platinum Full Synthetic 0W-50$$$6 quarts8,0000W-40Check price

The official Amazon-endorsed motor oil might be a surprise choice at first glance; how can it compete with established brands like Mobil 1 and Castrol? To be frank, Amazon doesn’t actually make the product; it buys it from another manufacturer and brands it as an Amazon product. 

Everything You Want

Overall, this synthetic oil does everything that a name-brand product would. Its affordable price and straightforward marketing make it a very appealing choice to buyers. All of this is backed up by the fact that it is a Best-Seller on Amazon; to be fair, it is an Amazon-branded product. Offering protection for at least 75,000 miles, this oil is valued as a very reliable and longevous product by buyers. Several users were impressed by the fact that it is a fully synthetic oil that matches the price of conventional motor oils. All in all, there’s really only one downside to this item: the insufficient fluid level lines on the bottle. Drivers often had to pour the oil out into a container that offered more accurate readings. Otherwise, this product is an unsurprising #1 for us. 

ProsCons
• High longevity
• Affordable
• Fully synthetic
• Perfect for high-mileage cars
• Insufficient clarity regarding fluid level
markings

Castrol is one of the most recognizable brand names when it comes to motor oil; its competition with Mobil 1 since the late 1900s has really pushed the availability of fully synthetic oils on the market. This product is geared towards maximum performance, and it certainly fits the bill.

Powerful and Safe

If this item could be summarized in a few words, it would go a little like this: more power, better performance, more frequent oil changes. Simply put, if you want something that does the job for months to come, you’re looking at our Editor’s Choice. However, if you’re looking to get a little extra performance, this Castrol oil is a fantastic option. With fluid titanium technology, it offers drivers incredible strength under pressure. It also protects your motor from viscosity breakdown and unwanted oil thickening. On top of that, it breaks the rule of thumb of changing your oil every 5,000 miles, offering up to 20,000 miles between changes. Suffice to say, this product is a beast.

ProsCons
• High-level performance
• Anti-breakdown engineering
• Fully syntheticHigher drain interval
• No significant downsides

Shell’s fully synthetic oil comes in as our third item, and it certainly holds its own against the synthetic oil titans like Castrol. This oil is a great choice, and goes toe-to-toe with its competitors.

All-Rounder

The Shell Rotella T6 offers minimal oil consumption—a silent but pesky problem that many drivers might notice. Compared to its peers, this oil is fantastic at resisting the general wear-and-tear that motor oil goes through over time. Many users were pleased to see that it does well to retain its viscosity, color, and overall level between oil changes. It is designed with the biggest engines in mind, yet can be perfect for the smallest VW. If you’re a truck driver that has had some issues with your oil in the past, the Rotella is a safe and solid option.

ProsCons
• Retains amount over time
• Anti-wear engineering
• Versatile and powerful
• Fully syntheticKeeps viscosity
• No significant downsides

While the Castrol GTX is advertised as a fully synthetic oil, it is actually up to 75% refined oil; despite this, it is a solid product. Using this in even the highest mileage engine will ensure your car keeps ticking like clockwork.

A Bit of Everything

The GTX series has been around since the late 1900s, offering buyers a premium-quality oil for an affordable price. While it does work very well, and is cheaper than its synthetic counterparts (such as Mobil 1 oils), the misleading marketing practices of Castrol have raised a few eyebrows among users. In fact, most reviews regarding this product are more focused on this issue than how well this product itself works. If you’re not overly concerned about getting fully synthetic oil, this product might just be a great choice. It offers great performance and longevity in engines of all lifespans, but do proceed with caution; if this product doesn’t meet your vehicle’s standards, you might be in for a surprise. Some buyers were disappointed due to the “ticking” that developed in their motor from using this oil.

ProsCons
• Great value for money
• Offers high performance
• Protects engine longevity
• Not fully synthetic
• Not compatible with all vehicles

As our fifth entry, we have the synthetic oil giant: Mobil 1. Its 0W-40 oil offers many advantages over some of its competition, including a longer lifespan and a more reliable performance.

Worth the Investment

While this item is a tad pricier than some other choices that promise similar results (the Castrol 03087, for example), it delivers in terms of quality and assurance. Mobil 1 is perhaps the most consistently reliable producer of synthetic oils, so it’s no surprise that one of their products makes it on our list. This oil in particular offers very high mileage compared to convention; manufacturer recommendations are anywhere from 10,000 to 20,000 miles (which is a bit extreme, to be fair) for every oil change. Buyers are often reluctant to take it that far, but even at 7,500 miles (well above the typical range of 3,000 to 5,000), this product keeps your engine running smoothly. If you’re not afraid to sink some extra cash for a quality product, this oil might be your answer.

ProsCons
• Quality engineering
• Fully synthetic
• Long interval for oil change
• Reliably looks after your motor
• Slightly more pricey

Valvoline is hardly the most recognizable synthetic oil brand. Despite the fact, this product is absolutely top notch, and easily deserves a spot here. On top of its functionality, the design and appearance of the bottle itself left many buyers pleased.

Thoughtful Presentation

First, let’s talk about the bottle itself; it boasts a very easy pour to ensure you don’t make a mess while changing your oil. It also has an easy-pull tab, a neatly-designed pour spout, and anti-glug tube—all of these features makes a routine oil change quick and simple. As for the performance, it doesn’t disappoint either. Valvoline guarantees that this product offers 50% more wear protection than industry standards (according to an IVA wear test). It helps maintain optimal fuel efficiency and is even designed to work at its peak in the harshest conditions. All in all, this oil is a solid choice; if you have no brand allegiance, the Valvoline fully synthetic line of oils are sure to keep your engine happy.

ProsCons
• Great presentation
• User-friendly
• Designed to withstand temperature
• Maintains engine and motor longevity
• Fully synthetic
• No significant downsides

One thing you might notice about this item is that it comes in 1-quart bottles. This means that if you want to get 5 or 6 quarts (as is convention), the cost will ramp up quickly. However, if you put the price aside, this oil performs as you’d expect any Mobil 1 product to.

Sturdy and Protective

Calling this oil tough would be an understatement. It is able to pour in temperatures as low as -53°F (-47°C), so unless you live in the Siberian tundra, you don’t have to ever worry about this oil freezing over. Its performance reflects its hardiness, with an impressive ability to maintain performance in harsher temperatures. It even improves on some other Mobil 1 products, as some buyers have noted. This oil is top-drawer in every department, from fuel efficiency to wear protection. There’s really not much to say about the 5W-50 version; if you’re not afraid to spend some extra cash for some top-shelf oil, do consider this product.

ProsCons
• Outstanding weather resistance
• Wear protection
• Increased fuel efficiency
• Fully synthetic
• Optimizes performance and longevity
• Very pricey

Pennzoil is a name that car enthusiasts will certainly recognize, as they are fairly competitive in the synthetic oil market. Their products are manufactured with a focus on longevity and keeping your car running at its best for years to come.

Quality Lifetime

The marketed qualities of this product are impressive and plenty. From temperature resistance to fuel economy, the Ultra Platinum brand of Pennzoil is meant to be the brand’s poster child. This oil aims to keep your engine as close to factory-new as possible, with sludge-protection and overall efficiency maintaining that idea. Pennzoil boasts that using this oil can save you 550 miles of fuel per year due to its efficiency, as well as keep your car running at its peak horsepower longer than other oils. Whether all of their claims are true is up to the buyer, but if even half of them are accurate, this product is top-shelf. Like the Mobil 1 oils, if you’re not afraid to loosen the pursestrings a little bit, be sure to consider this if your car requires a 0W-50.

ProsCons
• Temperature resistant
• Fuel efficient
• Keeps engine clean longer
• Endurance and longevity 
• Very pricey

Frequently Asked Questions

Q: How often should I change my oil?

A: It is generally recommended to change your oil between 3,000 and 5,000 miles, depending on who you ask. It’s not really that simple, however, as the type of driving you do daily can impact this number (start-stop traffic vs. road tripping, for example). Generally, you can tell it’s time to change your oil when it gets “goopy” or very dark brown, as this means it won’t give you peak performance. Otherwise, if it’s still very thin and runny, it’s (most likely) still perfectly fine.

Q: Does the type of oil filter matter?

A: Oftentimes, the oil filter you use in combination with a specific oil doesn’t really matter. That is to say, there won’t be any negative consequences of using one brand over the other. However, some brands recommend using their oils with their own oil filters (unexpectedly), as they are designed to work together smoothly. Check out your motor oil manufacturer’s product line to see if they have any recommended filters to pair it with.

Q: Can I safely mix conventional and synthetic oil?

A: Short answer: yes, you can. There won’t really be any functional issues if you mix different types of motor oil; in fact, some companies even dilute their own synthetic product with conventional oil and market it as fully synthetic. The downside, in this case, is that traditional motor oil is not as efficient as synthetic, and so will diminish the benefits you’d get from a purely synthetic product.

Conclusion — Buyer’s Guide

Well, there you have it: eight of the best synthetic oils on the market for your consideration. There are several categories to look at to really understand how you should be making your choice. If you’re limited by budget, there’s several options that might catch your eye—the Amazonbasics, Valvoline, and Castrol items may well be what you’re looking for.

As for technical limitations, if you’re in need of a thinner oil, there’s several options there, too. The Valvoline oil is a strong player in this regard too, followed by the slightly more viscous choices: Amazonbasics and the Castrol options again.

For a more powerful and thick option, Mobil 1 has you covered. Both of their products are quite thick (with the 5W-50 taking the cake) and are known to be quite resistant to any changes in temperature. In addition, the Pennzoil Ultra Platinum oil is one to consider, as long as you have some extra cash to splash on it. Finally, the Shell product we explored is a great all-rounder; it’s quite viscous without going overboard, and won’t put much of a dent in your budget.

As always, though, there might be one item that caught your eye from the first moment. Whether you need a specific type of oil or are looking for a specific brand, there might just be the exact motor oil you were hoping to find in this list.