Closeup of synthetic oil being poured

Oil is the lifeblood of your car. Without the right viscosity flowing through your engine, things would go south in a hurry. If you did nothing else but keep up the oil, odds are your engine would last far longer than you might expect. Simply put, it is the most important element of automotive maintenance. But which oil is the best oil?

First, let’s clarify the differences between synthetic and conventional oil. Conventional oil is organic, a direct descendant from the fossilized remains of prehistoric creatures. As these remains decomposed over thousands of years, they were turned into the black crude refined by ExxonMobil and the like. On the other hand, synthetic oil is made entirely of lab-created polymers.

If oil was anything like food, one would think that organic trumps synthetic. That’s not the case, however. Synthetic oil makes a significant difference to the health of your engine. For example, it provides superior mechanical performance, increased gas mileage, and reduced engine wear at extreme temperatures. While organic oil might last 3,000 miles between oil changes, synthetics can go 10,000 or more.

Our expert’s top pick for synthetic oil is Valvoline Advanced Full Synthetic Motor Oil, which offers excellent engine cleanliness through superior sludge and varnish protection.

Best Overall
Valvoline Advanced Full Synthetic Motor Oil
For the best in synthetic oils, it’s worth making the switch to Valvoline Advanced Full Synthetic.

While you’re changing your oil, don’t forget to also replace the oil filter.

Our Expert’s Top 5 Synthetic Oils

Here are the top oils on the market, as curated by our team of experts. Compare the ratings and features of the different brands to determine which is best for your engine and budget.

Editor's PicksBrandRatingFull SyntheticVarious WeightsChoice of Sizes
Best OverallValvoline Advanced Full Synthetic Motor Oil4.8
Best Budget BuyCastrol Full Synthetic Motor Oil4.8
Best for MotorcyclesCastrol Power RS 4-Stroke Motorcycle Oil4.9
Best for Diesel EnginesShell Rotella T6 Full Synthetic Diesel Engine Oil4.9
Best High MileageValvoline High Mileage with MaxLife Technology4.8

*Ratings are on a scale of 1 to 5 and based on reviews, feedback, and opinions of actual customers

Who Should Buy a Synthetic Oil

  • Those whose cars came with it from the factory. Luxury cars often require full synthetic oil, and most car manufacturers nowadays recommend synthetic oil. Always go with what your owner’s manual says.
  • Those who want to extend oil life. Synthetic oil can last anywhere from about 8,000-10,000 or more miles before requiring a change, whereas conventional oils generally only last about 3,000-5,000 miles.
  • Drivers in extreme climates. Synthetic oil helps keep your engine happy both in extreme heat and extreme cold. This is because they can withstand higher temperatures and flow better in cold temperatures than conventional oil.1 So there’s no need to swap a heavier-weight oil in the winter if you run synthetic.
  • Those who frequently drive short distances. Conventional motor oil may not warm quickly enough to burn off moisture and impurities if your trips are less than 10 miles apiece. Synthetic oil again is the better performer.

Who Should Not Buy a Synthetic Oil

  • Budget-conscious consumers. Synthetic oil costs about two or three times as much as conventional oil, so every oil change will cost more money. But you make up for it with longer durations between oil changes, so this is essentially a wash for most drivers.
  • Drivers who don’t travel far annually. If you have a second car that only sees a few thousand miles of sunny-day driving per year, synthetic oil might not be necessary. After all, oil still needs to be changed at least yearly regardless of oil type, so low-mileage garage queens don’t enjoy the advantages of synthetic oil.
  • Owners of older cars. Antique and vintage cars built before the era of synthetic oil might prefer traditional oil. If you own an older car, check out enthusiast forums for recommendations on whether synthetic oil plays well with an old engine.

Research Tips (from an Expert)

Keeping your engine happy and healthy is key to ensuring your car remains reliable, so don’t be flippant about the oil you choose. We’ve compiled everything you’ll want to keep in mind when shopping for synthetic oil:

  1. Check the weight of the oil. The weight of an oil is expressed using a numerical code system created by the Society of Automotive Engineers (SAE).2 Grades motor oils according to their viscosity. The higher the number, the thicker the oil, so 5W-30 is lighter than 10W-40. The W stands for winter and indicates the viscosity in cold weather, while the second number is representative of normal ambient temperatures. Check your vehicle’s owner’s manual to determine what weight of oil your vehicle needs.
  2. Look for additives. Many synthetic oils contain additional additives to help improve engine performance as well as detergents to help clean the engine. Check to see which additives are included in the oil you’re looking to purchase.
  3. Full synthetic or synthetic blend? If you want the higher performance of a synthetic oil without the consummate price point, a synthetic blend offers the best of both worlds. They perform better than conventional oils but don’t cost as much as full synthetic due to being partly blended with a traditional oil.3 They offer about 5,000 to 7,000 miles of engine protection before requiring a change.

How Much Do They Cost?

Between $20 and $50

For most synthetic oils, you can expect to pay between $20-$50 per five-quart container and still get a quality product. Full synthetics will cost more than synthetic blends but can last longer between changes. The additives used can also affect the price point. Gallon-sized containers of synthetic oil will obviously cost more than quart-sized bottles, but allow you to perform a complete change as opposed to just a top-up.

The Best Synthetic Oil: Full Reviews

Best Overall
Valvoline Advanced Full Synthetic Motor Oil
For the best in synthetic oils, it’s worth making the switch to Valvoline Advanced Full Synthetic.

Valvoline Advanced Full Synthetic Motor Oil is a great choice for drivers of all sorts, and exceeds industry standards for fuel economy and wear protection. It is available in a choice of sizes and features an easy-to-use plastic pull to cleanly remove the plastic seal.

Valvoline’s oil is suitable for use in extreme temperature conditions and boasts faster oil flow at start-up to help prevent cold starts. It contains a blend of innovative anti-wear additives for added engine protection. It also costs less than other popular synthetics like Mobil 1 or Royal Purple, ensuring that proper engine protection won’t break the bank.

Pros
  • Choice of sizes
  • Available in varying weights
  • Contains innovative anti-wear additives
  • Meets or exceeds industry standards
  • Easy pour bottle design

Cons

  • Some reviewers had issues with bottle leaking at delivery
  • Some packages missing “Advanced MST” designation

Best Budget Buy
Castrol Full Synthetic Motor Oil
For the best choice for budget-conscious consumers, look no further than AmazonBasics Full Synthetic Motor Oil.

Castrol Full Synthetic Motor Oil is a great option for the budget-focused consumer, as it comes in at around $20 per five-quart jug. It is available in a choice of container sizes and weights to suit various makes and models of vehicles.

It has been certified by the American Petroleum Institute for use with gasoline engines and helps to protect against engine wear while improving fuel economy. Castrol claims their oil was shown to perform four times better than other leading oils in the Sequence IVA wear test, which is an industry benchmark that measures an oil’s ability to inhibit camshaft wear. For the price, it’s a great choice that should provide excellent engine protection.

Pros
  • Manufactured in the USA
  • Helps reduce exhaust emissions
  • Prevents corrosive build up
  • Performed well in industry wear test

Cons

  • No clear visibility strip on the side of the bottle
  • Not rated for European cars

Best for Motorcycles
Castrol Power RS 4-Stroke Motorcycle Oil
Formulated to protect all 3 critical zones—engine, clutch, and gearbox.

For those on two wheels, the Castrol Power RS 4-Stroke Motorcycle Oil is a great pick and is available in a choice of three different weights. It has been formulated to protect all three major componentry sets— engine, clutch, and gearbox.

The race-derived technology is formulated to prevent viscosity breakdown and is intended to improve engine performance by reducing friction without any loss of lubrication. It’s a fast-flowing oil formulated to quickly circulate through your powertrain and provide excellent performance while exceeding API SL and JASO MA-2 standards.

Pros
  • Available in a choice of weights
  • Race derived technology
  • Shear stability prevents viscosity breakdown

Cons

  • Some reviewers found the packaging wasn’t leak-proof
  • Some reviewers felt this oil was too thin

Best for Diesel Engines
Shell Rotella T6 Full Synthetic Diesel Engine Oil
Rotella offers enhanced fuel economy capability without compromising engine protection.

The Shell Rotella T6 Full Synthetic Diesel Engine Oil offers enhanced fuel economy capability without compromising engine protection. Available in a choice of container sizes and weights, it is suitable for use in trucks and heavy machinery. It’s available in multiple sizes, including a five-gallon pail, making it perfect for fleet owners or those with large diesel machinery.

This oil has been engineered to control turbocharger deposits and emissions compliance, helping return better fuel economy. It also features super heat resistance to resist breakdown during operation. It meets API service standards as well as the performance requirements of several different manufacturers.

Pros
  • Variety of weights available
  • Triple protection plus technology
  • Enhanced with advanced additives
  • Offers enhanced fuel economy capability

Cons

  • Some reviewers found the packaging wasn’t leak-proof
  • Some reviewers noted their bottles didn’t come sealed

Best High Mileage
Valvoline High Mileage with MaxLife Technology
For high mileage engines, Valvoline High Mileage with MaxLife Technology has you covered.

For high mileage engines, Valvoline High Mileage with MaxLife Technology is an excellent option that is available in a choice of container sizes and weights. Boasting a thick anti-wear film, this oil is intended for use in engines with more than 75,000 miles.

It has been certified by the American Petroleum Institute for use with gasoline engines. Notably, it contains a blend of anti-wear additives, detergents, and seal conditioners to keep engines running at peak performance. Though it is a synthetic blend rather than a full synthetic oil, Valvoline’s MaxLife has been noted by reviewer after reviewer to slow or even stop leaks and also cut down on oil burning in older vehicles. For those with a car that’s less than new, this is the best choice out there. Plus, it only costs $18 for a five-quart jug to boot!

Pros
  • Enhanced anti-wear additives
  • Extra detergents
  • Premium seal conditioners
  • Exceeds numerous safety and performance standards
  • Excellent price point

Cons

  • Synthetic blend
  • Some reviewers found the packaging wasn’t leak-proof

Frequently Asked Questions

What is the difference between a synthetic blend and full synthetic oil?

The difference between the two types of synthetic oil is that full synthetic oil is made with 100% synthetic material, whereas a synthetic oil blend uses a mix of both conventional and synthetic oils. Blends offer better performance than conventional oils, but don’t cost as much as a full synthetic. It is important to keep in mind that a synthetic blend won’t last as long as a pure synthetic oil.

What oil is best for older engines?

Any high-mileage oil is your best bet, as it is specially formulated to care for engines with a lot of miles on them. Full synthetic oil is often a good choice for older engines, as it helps to reduce engine wear and deposit buildup that can become problematic, but there are some impressive synthetic blends on the market as well.

How long does full synthetic oil last?

Full synthetic oil can last anywhere from about 8,000-10,000 or more miles before needing to be changed, whereas conventional oils generally only last about 3,000-5,000 miles. Some synthetic oils even claim to be able to go up to 20,000 miles between drain intervals, though we’d probably be nervous going that long on the same oil.

What is the highest quality oil filter?

The highest quality oil filter is a high efficiency oil filter, as it allows for longer oil drain intervals thanks to its microscopic pores. Check an oil filter’s multi-pass filtering efficiency to get an idea of how effective it is at removing contaminants.

Article Sources

Ride Digest uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  1. Olsen P. Should you use synthetic oil in your car? Consumerreports.org. Published June 29, 2019. Accessed August 4, 2021.
  2. Hunting B. Understanding oil weight: What do the number on the bottle mean? Knowhow.napaonline.com. Published November 2, 2019. Accessed August 4, 2021.
  3. Advance Auto Parts. Synthetic blend vs full synthetic motor oil. Shop.advanceautoparts.com. Updated July 26, 2021. Accessed August 4, 2021.