Best Synthetic Oils: Invest in Your Engine’s Long-Term Health
What’s in your engine? Find out which synthetic oil is best for your ride
The Review Team
How We Decided
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PUBLISHED ON April 12, 2019
The engine in your vehicle is like an Olympic athlete’s body, composed of a network of components that must be kept in tip-top shape in order to achieve maximum results. Motor oil is the life force that courses through the engine, so you should use synthetic oil for optimized performance. Read on to see our picks for the best synthetic motor oil on the market.
- Best OverallMobil 1 Extended Performance 5W-30SummarySummary
The most trusted synthetic oil on the market, it delivers superior performance, efficiency, and longevity.ProsPros
Superb anti-wear performance in high temperatures, exceptional change interval, maintains long-term engine health.ConsCons
Pricey, containers can sometimes leak.
- Best ValueValvoline MaxLife High Mileage 5W-30SummarySummary
A bargain-priced synthetic blend oil that provides maximum protection for higher-mileage vehicles.ProsPros
Great performance for vehicles with high mileage, helps prevent oil leaks, sludge, and more, excellent price.ConsCons
Shorter change intervals, not recommended for lower-mileage vehicles.
- Honorable MentionRoyal Purple High PerformanceSummarySummary
The enthusiast’s undisputed choice for an ultra-high-performance synthetic motor oil.ProsPros
Fantastic for high-performance vehicles, maximizes fuel economy and extends change intervals, compatible with other types of oil for an easy switchover.ConsCons
Pricier than most brands, some reports of leaky containers.
Why Trust Us
All of our reviews are based on market research, expert input, and practical experience with each product we include. This way, we offer genuine, accurate guides to help you find the best picks.
Best Overall: Mobil 1 Extended Performance 5W-30
The best full synthetic motor oil in our comparison is the Mobil 1 Extended Performance. This premium synthetic oil offers unparalleled protection against engine wear, all-weather performance, efficiency, and longevity for automotive engines. That’s probably why most performance and luxury car manufacturers choose to run Mobil 1 in their cars right out of the factory.
Mobil 1 boasts incredible anti-wear properties in both extremely low and high temperatures, thanks to its SuperSyn Technology. This makes it a fantastic option for drivers in all types of climates. We were also impressed with the potent blend of cleaning and performance-enhancing additives found in this synthetic oil. You can expect a major boost in engine smoothness, responsiveness, and fuel-efficiency when you run Mobil 1 in your ride. Throw in the fact that users can expect to get up to 15,000 miles between oil changes, and you can easily see why we chose this for the best synthetic motor oil brand.
There are a few minor niggles, chiefly the high price tag this synthetic engine oil commands. In addition, there have been a few reports of consumers experiencing leaky bottles when stored over long periods of time. Still, if money isn’t an issue, then this could very well be the best motor oil on the market.
Best Value: Valvoline MaxLife High Mileage 5W-30
Although Valvoline MaxLife High Mileage is technically a synthetic blend oil, it won the best synthetic oil value spot in our comparison because it offers an impressive blend (pun firmly intended) of protection, performance, and value for higher-mileage engines.
This is an excellent option for vehicles with more than 75,000 miles on the odometer. It’s formulated with special seal conditioners, anti-wear additives, extra detergent technology, and an array of antioxidants to boost long-term engine health. This proprietary formula helps reduce oil leaks, sludge, and poor-running engines in high-mileage cars. The fact that this synthetic oil blend has an enticingly low price point made it the clear winner for this category.
Complaints are few, but worth noting. The average oil change interval for this brand is anywhere from 5,000 to 7,500 miles, shorter than full synthetic oil brands, though this is to be expected for a blend. Additionally, Valvoline MaxLife is specifically engineered for vehicles with over 75,000 miles, so this may not be the best oil for your ride if it has lower miles.
Honorable Mention: Royal Purple High Performance 5W-30
Royal Purple is a renowned full synthetic oil brand among auto enthusiasts and racers everywhere, and this oil definitely delivers optimal performance. The secret behind Royal Purple’s superior performance is its Synerlec additive. This additive works on a molecular level by generating extra-strength ionic-bonds with the metal surfaces in your car’s engine.
The oil responds with increased viscosity, strength, and lubricity, so your engine performs at its prime—even under extreme stress. This makes it a wonderful choice if you have a lead foot, race your ride, or simply want maximum engine performance. You can expect an increase in fuel-efficiency and oil change intervals. Initially, you’ll have to change the oil at 3,000 miles when switching over to Royal Purple, but you can enjoy 7,500 to 10,000 miles between oil changes afterward.
This high-performance motor oil has a few shortcomings. If you’re on a tight budget, its higher-end price may push you over the edge. Also, there have been some cases where the containers leak if stored for extended periods. With that said, if your blood type is 5W-30, and your engine sees its redline multiple times per day, this is perhaps the best synthetic motor oil you can get for your needs.
Best High-Mileage Synthetic Oils
- Best OverallAmazonBasics High-Mileage Motor OISummarySummaryA good, affordable option for older vehicles needing some extra lubrication.ProsProsGood for vehicles over 150,000 miles on the odometer. Can be changed every 5,000 miles.ConsConsProduces an awkward smell when first opened.
- Best ValueCastrol's GTX High-Mileage OilSummarySummaryGood results for a lesser known brand name. Good for vehicles above 75,000 miles.ProsProsGood general performance. Engine parts run more quickly and more smoothly.ConsConsNo clear or opaque surface on the bottle to measure inside oil levels.
- Honorable MentionValvoline High-Mileage with MAXLIFESummarySummaryA high-performance, high-mileage oil that is more of a premium blend than other options.ProsProsGood for cars above 75,000 miles. Helps to reduce oil burnoff, sludge buildup, and more.ConsConsOil burnoff resistance decreases after 1,000 or 2,000 miles with the oil.
Best Overall: AmazonBasics High-Mileage Motor Oil
AmazonBasics has been making a name for itself when it comes to products that offer performance and results equal to name brand items at a fraction of the cost. For high-mileage oil, the brand's 10W-30 oil may seem like a risk, but it actually does a good job of keeping parts running smoothly without too much wear and tear. Meant for vehicles that have 75,000 miles or over on them, the oil is formulated to resist common break down and premature wear.
Performance is rather straightforward and ordinary. It is easy to apply and leaves engine parts running noticeable quieter and smoother. The container is also easy to handle and comes in a few different size options for finding the right amount for your vehicle. Unfortunately, the container lacks a clear or opaque surface, for the included level gradients are difficult to use when measuring the remaining oil after use.
Best Value: Castrol's GTX High-Mileage Oil
Castrol's GTX High-Mileage Oil is a standout option for older vehicles that need some extra help running when engine parts are starting to wear down. The blended oil has a good amount of durability and protection to resist burn-off and viscosity breakdown. More importantly for a high-mileage oil, it also helps to fight against sludge build-up and prevent failure of parts like the emission system and the catalytic converter.
This oil has a very good track record with engines that have mileage counts of around 150,000 miles. It works well with general engine maintenance and can be replaced every 5,000 miles without the worry of wearing out too early. The only major issue with the oil is a not-too-common smell that comes from the container. It's a personal matter, but you may find the smell to be overbearing when working in a closed-in environment.
Honorable Mention: Valvoline High-Mileage with MAXLIFE
As a high-performance, high-mileage oil, Valvoline MAXLIFE oil sits on the premium side of life-extending oil options available on the market today. Meant for cars with over 75,000 miles on the engine, the oil is formulated to protect or repair common old engine issues such as seal leaks, oil burnoff, deposit and sludge buildup, and more. As a synthetic blend, the oil offers a lot of longevity with less wear than other competitors above the 5,000-mile mark after an oil change.
This is one of a few high-mileage oils that actually perform well if you change it every 10,000 miles instead of the usual 5,000. While it's not necessary to extend the oil change frequencies, the longevity of the oil does make it more convenient if you want to keep oil changes down as much as possible. Noticeable performance gains remain for several thousands of miles, but the oil burnoff can lead to a reduced amount of 1,000 or 2,000 miles after the latest oil change.
Best High-Performance Synthetic Oils
- Best OverallValvoline VR1 Racing OilSummarySummaryA good racing oil that is meant for weekend racers and daily commuters alike.ProsProsHigh zinc and phosphorus blend for anti-wear properties. Good burn resistance.ConsConsNot as good for high-mileage vehicles as more dedicated options.
- Best ValueCastrol EDGE Extended PerformanceSummarySummaryAn all-around high-performance oil that does well in racing conditions.ProsProsLarge bottle with multi-case options available. Long life of around 10,000 to 15,000 miles.ConsConsMore suitable for long race conditions than short, fast races.
- Honorable MentionBrad Penn Oil Partial Synthetic Racing OilSummarySummaryA racing oil that has good results for other high-performance conditions like towing and hauling.ProsProsA good degree of resistance against viscosity and thermal breakdowns.ConsConsMore expensive than other general oils. Not as good as dedicated racing oils.
Best Overall: Valvoline VR1 Racing Oil
Valvoline's VR1 Racing Oil has almost everything true weekend racers need out of a high-performance oil while retaining a high degree of compatibility with everyday engines. While some racing oils are meant just for the rough conditions of a race, this one offers a good balance between the durability necessary to survive and the formula necessary to help most engines stay running for longer.
The formulation comes with a high content of zinc and phosphorus to extend the normal anti-wear properties of other high-performance oils. As a racing oil, it is compatible with gasoline blends that use partial or full amounts of alcohol as well. The burn resistance is good, and the formula works equally well for high-mileage vehicles as it does in racing conditions. However, a true high-mileage formula is recommended if you want the best results in terms of longevity for older vehicles.
Best Value: Castrol EDGE Extended Performance
This isn't necessarily a true racing oil like other offers, but Castrol's EDGE Extended oil has enough long-term performance results to make it worth a go if you are a weekend racer. In other words, the oil does a good job of performing well in general racing conditions and can be used for other transportation needs like everyday driving and towing/hauling. This makes it a good option for anyone who uses their high-performance car as a daily commuter as well.
The oil comes in a 5-quart bottle and is available in large case packs for better value and bulk. The "extended performance" part of the oil comes from the formula's longevity that's designed to last up to 20,000 miles before needing a change. While the lengthy oil change span may be too idealistic for some older vehicles, it is easy to expect the oil to last 10,000 to 15,000 miles without showing major signs of degradation, break down, or burn off. For racing conditions, the "extended performance" is more suitable for long racing conditions more than challenging conditions that rely on pure speed and performance from the engine.
Honorable Mention: Brad Penn Partial Synthetic Racing Oil
Brad Penn's partial synthetic racing oil is a good all-arounder option for weekend racers or vehicle owners who use their rides for towing and hauling. The oil performs well in conditions where the engine and individual components are under high loads of torque and pressure to perform. There is also a small noticeable boost in engine efficiency and horsepower output but not as much as true racing or high-performance oils designed to get the most out of the engine in terms of power.
The oil has a high degree of resistance and protection against most oil issues like thermal and viscosity breakdowns. Its longevity is equally useful in high-performance driving conditions as it is with older, high-mileage vehicles that need extra protection from common wear and tear. Given the price of the oil, however, it doesn't offer the most in terms of value compared to true budget options that exist in the high-performance oil niche.
Best Synthetic Oils for Diesel Engines
- Best OverallAmazonBasics Full Synthetic OilSummarySummaryOne of the best diesel synthetic oils that offer a good balance of performance results and value.ProsProsNoticeable performance gains that last beyond the 5,000-mile mark. Compatible with different engine types.ConsConsSlower-than-average rap up. Not suitable for racing conditions.
- Best ValueShell Rotella T6 Motor OilSummarySummaryHigh-quality performance at a low cost; this synthetic oil stands out as a money-saving option.ProsProsGood resistance to viscosity and thermal breakdown, sludge buildup, and oil burnoff.ConsConsNo clear window to measure leftover oil with the included level markings.
- Honorable MentionValvoline Premium Blue OilSummarySummaryThe best choice to consider if you want to buy synthetic oils for diesel engines in bulk.ProsProsComes in 1-gallon and 3-case options. A good amount of oil for larger engines. Designed for extreme temperatures.ConsConsQuality of the case is lackluster. Cases can come from the factory with a broken seal.
Best Overall: AmazonBasics Full Synthetic Oil
AmazonBasics' heavy-duty diesel and gasoline engine oil do what you'd expect from any diesel oil: It coats engine parts well to reduce friction and wear. While it doesn't stand out in terms of performance or longevity, the fact that it delivers standard performance at a low cost is where it shines. The performance of the oil comes with a lot of money-saving value that other equal competitors often lack in their own offerings.
The formula is designed to protect itself and engine parts from extreme wear that's common with heavy-duty use. It does well in cold weather, has a good level of resistance to viscosity and thermal breakdown, and has decent burn-off resistance. The design of the container is somewhat lackluster and variable, however. For example, some cases come with a clear window to measure leftover oil after use, while others lack the window, making it difficult to see how much oil is left.
Best Value: Shell Rotella T6 Motor Oil
Shell's Rotella T6 Diesel Engine oil is somewhat unique in that it offers the performance results of higher-priced options with the money-saving value of budget options. The formula of the oil is engineered to work with both gasoline and diesel engines, with a special focus on high-torque, high-stress conditions many heavy-duty vehicles like full-size trucks may encounter on the road. At the same time, its plethora of sizes and bulk options means you can buy more for less to get some extra savings.
High-performance gains tend to last beyond the 5,000-mile mark, and the formula works well in engines that have more variation in certain properties like temperature. The oil also works well in different types of engines, including some motorcycle engines. It can also be used on high-mileage engines to reduce the noticeable "clinks" and "bangs" that tend to arise with age. For the most part, the only downside to this oil is a slower-than-average rap up and performance results that aren't quite suitable for racing conditions since the oil can break down more quickly in extreme racing conditions.
Honorable Mention: Valvoline Premium Blue Oil
If you need a lot of diesel-use oil, Valvoline's Premium Blue Extreme Synthetic Oil is hard to beat in terms of sheer quantity and value. Coming in 1-gallon and 3-case packages, the oil shines a lot when it comes to buying in bulk. Each container offers plenty of oil for a single change on larger engines or several changes on smaller engines. Combined with decent protection and performance-boosting properties, this one is hard to beat as a general diesel all-arounder.
The oil is designed for the extremes, which in the mind of Valvoline, means hot and cold conditions. The oil offers good results in freezing temperatures and with cold-weather starts. For hotter temperatures, it resists degradation so the friction reduction coating doesn't break down over time. The size of the container and multi-container package options make it a perfect fit for large vehicle owners. The quality of the case, however, is a bit hit or miss; some have reported that the bottle comes from the factory with a broken seal.
Best Synthetic Oils for Motorcycles
- Best OverallRavenol Four-Stroke OilSummarySummaryOne of the best synthetic oils to choose for four-stroke engines. Noticeable gains with on- and off-road use.ProsProsEngine noise reduction is noticeable. Small gains in horsepower and fuel efficiency.ConsConsPerformance gains are no different than other brands. The real value is from the low cost.
- Best ValueCastrol POWER Synthetic OilSummarySummaryA good synthetic oil designed for larger, more powerful bike engines used in high-performance riding.ProsProsGood improvement with shifting quality. Cooler running temperatures.ConsConsVariable results depend on the engine type. The longevity of the oil is shorter than other options.
- Honorable MentionMobil 1 Racing 4T OilSummarySummaryFor racing-specific conditions, this is the motorcycle oil to choose. Good for competitive environments on and off of the road.ProsProsGood results. Easy application with straightforward bottle design.ConsConsQuality of the container is lacking; leaks and seal breaks are somewhat common.
Best Overall: Ravenol Four-Stroke Oil
Designed for general four-stroke engine use, Ravenol's Motorbike oil is marketed with having the "latest lubrication from Germany." While that doesn't mean much, the oil actually has some noticeable gains it offers when applied to an on- or off-road engine that needs extra lubrication to perform well under extreme conditions. This means it's a good solution for high-speed bikes or off-road engines that take a lot of abuse out in the wild.
The general efficiency the oil delivers tends to be noticeable right from the start after a change. Engine noises go quiet, shifting performance gets smoother, and some users even report slight gains in horsepower and fuel efficiency. While this oil won't work magic on a neglected or old engine, it offers just enough to take a normal four-stroke engine over the edge in terms of performance and efficiency. With that said, results are akin to other competitors, so the real draw of the oil is with its relatively low price tag.
Best Value: Castrol Power Synthetic Oil
Castrol's Synthetic Motorcycle Oil is designed for larger, more powerful bike engines that get used near the limits of their capabilities (i.e. the points where the parts experience the most wear and tear. Suitable for four-stroke motorcycle engines, the oil's formula has a good balance of part protection and performance gains, so you can buy this oil with the expectation of getting some noticeable signs of performance enhancements.
Slight signs of improvement include smoother shifts and cooler running temperatures, especially when the engine is running at high speeds or for long periods of time. The exact level of improvement will depend on the engine itself and how you use it, but most happy customers report seeing noticeable effects almost immediately after application. The longevity of the oil, however, lacks compared to other motorcycle oil options. Smooth shifting tends to go first, so frequent and routine oil changes will be necessary to maintain the performance gains.
Honorable Mention: Mobil 1 Racing 4T Oil
If you need a general racing formula in a motorcycle oil, Mobil 1's Racing 4T oil is hard to beat. Designed for extreme riding conditions, particularly off-road and competition driving, the oil offers noticeable results quickly in key areas like smooth shifting and temperature stability. In on-road driving conditions, the oil also does a good job of extended basic engine part protection so things like the transmission tend to last longer than with normal or value motorcycle oil options.
Beyond the performance gains, there is also something to be said for the oil's bottle design. Featuring an easy to open cap that still offers a tight grip when not in use, the bottle is easy to use for a quick oil change. More importantly, the side window allows you to measure the amount of remaining oil after a change. The quality of the container, however, isn't as consistent as some other brands; it's not uncommon for some bottles to come with leaks or clear breaks around the cap in the shipping container.
Benefits of Synthetic Oil
- Extend engine life. The best synthetic motor oil is formulated to have a high degree of natural solvency, meaning it can clean and remove deposits. This keeps your motor sludge- and deposit-free so it can run as smoothly and efficiently as possible, as well as extend the lifespan of engine seals and other components.
- Maximize engine performance. There’s a reason why high-performance vehicles and race cars all run synthetic oil from the factory—superior engine performance. Enthusiasts often report that they perceive more power and torque from their engine when they use synthetic oil. At the very least, synthetic oil is slicker than conventional oil, so it’ll definitely make your ride run smooth as silk.
- Improve fuel mileage. Premium synthetic oil reduces the amount of friction that occurs between key engine components, therefore making your engine run smoothly and efficiently. Theoretically, this increases the fuel mileage of your vehicle, so you’ll spend more time on the road and less time (and money) at the pump.
- Flows better in cold or hot weather. The proprietary formula of synthetic motor oil makes it flow better in extreme temperatures. During wintertime, its resistance to viscosity breakdown lets it flow freely regardless of how cold it is outside, so your car is less likely to break down due to cold starts. Alternatively, synthetic oil works at peak performance during hotter weather too.
- Longer lifespan than conventional oil. The best fully synthetic motor oil has a considerably longer lifespan than synthetic blends or conventional oil. In some cases, full synthetic oil has a change interval of up to 15,000 miles, compared to 3,000 miles for conventional motor oil.
- Saves you money in the long run. Although going synthetic initially costs more per quart than conventional, it actually saves you money in the long run. Not only will you get more mileage out of engine components and save money on fuel, but you’ll also enjoy savings on less frequent oil changes. That’s something every motorist can get revved up about.
Types of Synthetic Oil
Full synthetic motor oil is created in a laboratory with a unique molecular structure and is infused with additives to deliver optimal wear protection and performance for your engine. Unlike conventional oil, it is not derived from whole crude oil, so it’s formulated without any of the impurities that you’d find in conventional oil. The best synthetic engine oil brands use a proprietary blend of anti-wear and cleaning additives to make your motor run at its best.
As the name implies, a synthetic blend motor oil is a mix of conventional oil and a brand’s synthetic base oil. Think of synthetic blend oil as a conventional oil fortified with synthetic supplements for better engine protection and performance. However, it’s worth mentioning that synthetic blends do not deliver the same caliber of performance and protection that a best-rated synthetic oil does. Still, if you choose not to spend a little more for full synthetic oil during your next oil change, you can rest assured knowing that a synthetic blend provides more benefits than conventional oil.
Founded in 1957, Liqui Moly is a German company that manufactures oils, lubricants, and additives. The brand prides itself on offering premium quality products at a more accessible price point than its competitors. One of its top products is the Liqui Moly Longtime High Tech 5W30 Synthetic Oil.
Introduced in 1974, Mobil 1 offers synthetic motor oil and lubricant products. Its synthetic motor oil is perhaps the most recognized brand in the business, with prestigious auto manufacturers such as Porsche and Mercedes-Benz using Mobil 1 synthetic oil in all their vehicles. One of its best-selling products is the Mobil 1 Extended Performance 5W-30.
Established in 1986, Royal Purple is an American manufacturer of lubricant products for automotive, industrial, marine, motorcycle, and racing usage. It is best known for its motor oil products and garners the endorsement of car enthusiasts for its high-performance formula. A particularly popular product is the Royal Purple High Performance 5W-30.
Synthetic Oil Pricing
- Under $30: You’ll find a few options for under $30 for a 5-quart container, though most of these products are synthetic blends. Not all value-priced synthetic and synthetic blend motor oil brands are created equally, so make sure you scour our synthetic motor oil reviews to see which one fits your needs.
- $30-$39: The majority of synthetic motor oil products fall within this price range. You’ll find everything here, from high-performance motor oil to high-mileage oil. These options typically deliver a great mix of performance, efficiency, and value.
- Over $39: Some of the best engine oil in the world resides in this lofty price point. These premium synthetic oil products promise the best engine protection, performance, and efficiency.
Viscosity grade is the most important factor in selecting the right synthetic motor oil for your needs. If you operate your car in a hotter climate or ring your engine out often, a viscosity of 10W-40 is best. For commuting in most warm or cold climates, a 5W-30 synthetic oil fits the bill. Finally, if you drive in conditions that could be described as arctic, a 5W-20 or even 0W-20 synthetic oil is advisable.
The labels on all types of synthetic oil list the specific application that the oil is designed for. Some common synthetic oil applications include higher mileage, extended performance, diesel engines, and motorcycles. Do your homework on your vehicle’s condition before you purchase the best synthetic oil for your needs.
Compatibility with Existing Oil
Before you add full synthetic engine oil to your ride, it’s important to note if the brand is compatible with other types of oil. If it isn’t, you’ll have to drain the existing oil before filling it up with the synthetic stuff. It’s also crucial to consult your owner’s manual to verify which type of oil your vehicle requires. For instance, most vintage vehicles were engineered to run best on conventional oil.
Each synthetic motor oil brand adds its own proprietary blend of additives to enhance certain properties. For instance, viscosity-index improvers work extremely well in ensuring that oil doesn’t get too thin at higher temperatures. Other additives like detergents are efficient cleaning agents designed to remove deposits and sludge from your engine. Determine which additives would provide the benefits you need the most before purchasing a synthetic engine oil.
- Price: If you’re on the fence about plunking down the price premium that certain high-end full synthetic oil brands command, it’s completely understandable. Expensive synthetic oil brands aren’t always objectively superior to less expensive brands. Conduct your own synthetic oil comparison and research reviews online to determine which synthetic oil is right for you.
- It’s important to carefully read the label of synthetic motor oil containers. These labels list essential information about the synthetic oil viscosity rating, application, and, sometimes, the additives it contains.
- Look for an American Petroleum Institute (API) rating donut somewhere on the synthetic oil container label. This seal of approval means that the synthetic engine oil has passed the API’s rigorous quality standards. To learn more about the API oil categories, click here.
- Before switching over to full synthetic oil, consult your vehicle’s owner manual to see if there are any break-in instructions to prep for the switchover. Also, make sure that the synthetic oil you intend on using is compatible with other types of oil. If it’s not, you’ll have to completely drain your existing oil before going full synthetic.
- If you’re not afraid to get your hands dirty and change your car’s oil yourself, ensure that you don’t overfill your engine’s crankcase with oil. Overfilled oil can rinse into the crankcase and cause air bubbles to churn into the oil. This can stress the engine components, cause overheating, and even foul the spark plugs.
- Check your oil at every other gas-up. For best results, run your car for 15 minutes then park it in a level place. Let it cool down for 15 minutes, remove the dipstick and wipe it with a clean rag. Reinsert the dipstick all the way, then pull it out to ensure the oil level is between the marks.
- If you plan on doing a lot of towing or racing with your vehicle, consider adding an oil cooler if your ride isn’t already equipped with one. Oil coolers function the same way your radiator does and can dramatically increase the lifespan of your engine.
Q: What does API SM/CF and SL, SJ, SH, SG mean on my oil container?
A: API sets industry-recognized standards for oil and petroleum products for passenger and commercial vehicles. The letters after API, like SM or SL, denote the quality of motor oil. Currently, the highest standard for passenger vehicles is SN. CF denotes a diesel engine or commercial vehicle standard, and the highest standard is CJ-4.
Q: Will I damage my engine if I switch from synthetic to conventional oil?
A: No, although you’ll experience a perceivable loss in protection, performance, fuel mileage, and longevity if you switch back to conventional oil. Be aware that some synthetic oil types aren’t engineered to be mixed with other oil types, so in this circumstance, you’ll have to drain your existing synthetic oil before adding any conventional oil.
Q: Do unopened bottles of synthetic oil have an expiration date?
A: This largely depends on the individual manufacturer of the synthetic engine oil. Some brands claim that unopened containers of their synthetic motor oil have a virtually unlimited shelf life if stored under ideal conditions. Alternatively, other brands like Mobil 1 claim that unopened containers of their oil last up to five years. Read the label of your synthetic oil container for this information and always follow the manufacturer’s expiration date.
Q: Will synthetic oil cause my engine to consume more oil?
A: This is another commonly-cited myth about synthetic motor oil, and it’s also false. Synthetic engine oil in no way causes your engine to consume more oil compared to conventional oil.
Q: Is it true that some synthetic oil brands can last up to 15,000 miles?
A: Thanks to the innovative additives and other properties of modern synthetic motor oil, you really can follow the manufacturer’s recommended oil change interval without inflicting any harm on your engine. Note that the exact oil change interval may vary depending on your particular vehicle, so always consult your owner’s manual to make sure it doesn’t have a different recommended oil change interval.
The best synthetic oil in our comparison is the Mobil 1 Extended Performance 5W-30. It offers an unbeatable combination of superior anti-wear performance in all climates, amazingly long oil change intervals, and exceptional additives for maximum fuel-efficiency and long-term engine health.
Our budget-friendly pick is Valvoline’s MaxLife High Mileage 5W-30.