How Quickly Can Engine Oil Go Bad, And Does It Expire?

Semi-regular oil changes are (or should be) a regular part of car ownership, with some drivers going to a mechanic for the service and others opting to do it themselves. Changing your own oil comes with a few considerations beyond the act itself.

There are several brands of oil to choose from, as well as different oil types intended for different kinds of engines, environments, and so on. You'll want to be sure to pick something that works well with your car's particular internals. But since oil changes happen so infrequently — changing it out every 5,000 to 10,000 miles is recommended – you could find yourself with a bottle or two of unused engine oil for an extended period.

Just how long can that oil sit there before it needs to be disposed of? Is it safe to use oil that's been sitting on the shelf for a year? Do dates matter for engine oil in the first place? A bottle of oil (opened or not) that's been sitting around for a year or two is likely still okay for you to use, but there are some notable exceptions you need to keep in mind.

In a nutshell, yes, engine oil can and does expire, whether you're using it or it's being stored outside of a vehicle. Exactly how long that takes is highly variable, though.

Many factors contribute to engine oil shelf life. Synthetic oils (a mixture of refined oil and several other compounds) have an average shelf life of up to eight years. Conversely, conventional engine oils are "rougher" on a molecular level and tend to break down faster, with an approximate shelf life of up to five years.

Those estimates can also vary based on whether or not the container has been opened. Whether your oil is fully synthetic, a synthetic blend, conventional, or monograde also makes a difference. Opening the bottle but not putting the cap back on tight enough (or at all) will speed up degradation as well.

Your choice of storage environment also matters. Ideally, you should keep your bottles of engine oil in a clean, dry, safe location (away from children and pets, away from food, etc.) where the temperature won't drop below 40 degrees Fahrenheit or go above 85 degrees. Under these conditions, oil can remain viable up to, if not a little past, its estimated shelf date. Otherwise it will likely lose effectiveness much sooner.

If you're not sure about the condition of your oil, there are ways to check that don't require pouring what could be expired fluids into a combustion engine. If you're uncertain about a given bottle of oil, even if it appears to be okay, it's recommended that you avoid using it anyway to be on the safe side. It's better to buy a new bottle than risk damaging your engine.

The quickest way to tell if unused oil — that is, oil that hasn't been run through an engine — is still good is to check the printed shelf date. If it's past that date, don't use it. If there is no shelf date on the bottle, you can estimate one by finding the production date and adding five (for conventional) to eight (for synthetic) years onto that. This applies whether the bottle is still sealed or has been opened, so long as the oil was never used.

For used oil, it's more a matter of how it looks. Dark brown or black oil is most definitely breaking (or already broken) down, while fresh oil has more of a light brown or amber color to it. Similarly, viable oil will have a smooth, well, oily texture to it while degraded oil will be much thicker, viscous, and possibly even gritty.

Popular Synthetic Oil Brands Ranked Worst To Best

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The bane of nearly every motorist's existence is the simple oil change. Sure, we all know we need to get it done, as we're often told by the vehicle itself — not to mention our mechanics and our parents — that it's a necessary evil. Still, it's a bit of a chore, and the fear of an aggressive upseller at the lube shop is always looming.

Many vehicles produced today require full synthetic motor oil to be added when the used stuff is changed out. In an effort to help both do-it-yourselfers and car owners presented with a bevy of options at the shop, we've ranked ten of the most popular brands of synthetic oil. While all oils meet quality standards set by the American Petroleum Institute, we've ranked them by more intangible qualities -– things like user reviews, warranty information, brand recognition, and more.

If you're looking for an oil filter to go with that oil change, SlashGear has you covered with our list of the best oil filter brands. Further, if a broader motor oil brand ranking is something you might be interested in, we've got one of those lists as well. 

One last note — we've linked five-quart jugs of 5W-30 Full Synthetic oil with our descriptions, but it's important to note what weight and amount of oil is required for your specific vehicle. That information can be found in the owner's manual and usually on the engine's oil fill cap as well.

If one is just looking to get some oil in the engine because that light that most folks don't recognize anymore — it's an oil can — has kicked on, AmazonBasics fits the bill with a practically-generic product. The company that started with books and might be getting into the mobile service industry soon took on the motor oil business in 2018.

Expectedly, Amazon's self-branded oil costs less than any of its competitor's synthetic offerings on the site, but it's not a terrible option by any means. In fact, it's well-regarded among drivers who have trusted this newer offering in their cars' engines.

At under $25 for a five-quart bottle, it's unsurprising that Amazon's oil has over 25,000 ratings and 4.8 stars on their website — as long as those vehicles using the oil aren't seizing up or exploding, drivers are likely to consider the savings more than enough of a reason to leave a five-star review. However, even after a little research, AmazonBasics oil is still proven to be a reliable product. Independent YouTube videos testing its properties prove Amazon holds its own against other brands in a number of different situations. While these tests are in no way definitive, they should encourage users who doubted the quality of the product to give AmazonBasics a shot.

Volkswagen. Renault. GM. These are just a few of the auto manufacturers who trust their engines to stay lubricated with Motul products, and Motul responded to that trust by making specific lines of motor oil for each of those automakers. The company has also been recommended by Honda, Hyundai, and Toyota — the list of manufacturers goes on and on.

The French motor oil company is perhaps best known for its applications in motorsports, but Motul is just as comfortable in the DIY and daily driver arenas. Its various lubricants of oil are recommended by manufacturers, technicians, classic car restorers, and heavy machinery operators. Motul's variations on its 8100 line, much like their Specific lines for individual manufacturers, feature distinct formulations of motor oil for different engines.

A 4.9 star rating on Amazon from more than 1,500 ratings proves that many drivers are willing to pay more for a quality product, and Motul has demonstrated that its formulations provide superior performance for customers.

An independent American oil company founded by a former fighter squadron commander, AMSOIL created the first synthetic motor oil that met the American Petroleum Institute's service requirements. AMSOIL's lineup of all-synthetic motor oils now goes above and beyond the American Petroleum Institute's standards, providing 75% more engine protection against wear and horsepower loss.

AMSOIL is not cheap -– a gallon of 5W-30 is almost $90 on Amazon – but the company's high quality standards have earned it a 4.7 star rating and many positive reviews on that website, and over 4,500 reviews and a 5 star rating on their own store site. AMSOIL also offers a guarantee of 25,000 miles or a year from installation, with no restrictions on that warranty based on the mileage of the vehicle in which it is installed. 

Additionally, for buyers who put importance on the source of their purchases, AMSOIL is formulated, blended, and packaged in the United States.

One of the oldest brands on our ranking, the Quaker State name was first used in 1912 when the Phinny Brothers Oil Company of Oil City, Pennsylvania, wanted to use a title for their brand that stood out among competitors. Despite changing hands a few times –- most recently when it was purchased by Shell in 2002 –- Quaker State has retained its brand name and reputation since the beginning of the 20th century.

In 2014, Quaker State was rewarded for its years of positive branding and high quality product with a branding relationship with Hyundai. The Korean automaker agreed to carry and install only Quaker State oils in its new vehicles and in dealership service locations.

Quaker State, with its recognizable green-and-gold packaging, has one of the best warranties in the business. Since 2011, the oil company has been rewarding users of their specialty motor oils, including full synthetic, with a cash bonus if their vehicle goes from under 75,000 miles to over 300,000. There are, of course, conditions that apply, but the company does have a Hall of Fame on its website that features several "Cash Back Bonus" qualifiers. The brand has even inspired a chain of gas stations-turned-restaurants called Quaker Steak and Lube!

Shell PLC is the fifth-largest oil company in the world and second only to Exxon Mobil Corp on the New York Stock Exchange. Shell owns a variety of brands and products ranging from gasoline to coolant to lubricants for electric vehicles and transformers. Not bad for a company that started out importing seashells for collectors — hence the shell logo – in 1833.

Since our focus today is synthetic motor oil, we'll take a look at Shell's Rotella line of synthetic oils. Lube techs across the nation know Rotella as one of the most popular diesel oils on the market, a clean and reliable full synthetic oil that can be used in both diesel and gasoline engines. Customers frequently bring their own cases of the dependable oil with their diesel trucks, and fleet managers appreciate the ability to use Rotella in both gas and diesel engines as a cost-saving option. 

While Shell PLC is the owner of several of the brand names on our list, Rotella is one of their best-known products under their own label.

While other oil brands on this list are well known, Royal Purple is one that's always been popular but also flies a bit under the radar. People in the know, however, are always willing to testify on the benefits of the purple powerhouse known as Royal Purple.

It's a company that's been producing motor oils since the 1980s but only began selling motor oils for consumer use in 2003. Royal Purple's pedigree in both industrial use and motorsports gave it a great reputation even before motorists began using its products, and its decision to add a purple dye to the oil definitely made the product seem more unique when compared to other engine lubricants.

Royal Purple's brand of synthetic motor oil, which is enhanced with a trademarked blend of additives, is reasonably priced, well regarded, and sports a 4.9 star average on Amazon with nearly 4,000 ratings. That's a lot more than just a crazy color on an average product –- that's Royal Purple combining savvy marketing with great synthetic motor oil.

A company founded in 1913 with origins in Pennsylvania, Pennzoil is one of three brands on our ranking under the larger Shell banner. Pennzoil's synthetic oil line is unique in that it's made with natural gas rather than crude. That base oil, according to the company, has fewer of the impurities found in the crude base other companies start out with. The result is a line of synthetic oils that are purported to keep pistons cleaner, deliver better fuel economy, and work better in extreme temperatures.

Pennzoil's full synthetic offering features a 4.8 star average on Amazon and an impressive ratings count of nearly 11,000. The company's century-plus history, along with the claim that using Pennzoil will protect for 15 years and add an extra 550 miles per year on average, contribute to customers' loyalty and willingness to share their success stories with others. Despite all these benefits, the price range for even Pennzoil's high-end Ultra Platinum motor oil line is still markedly lower than several of its competitors' products.

Motor oils, generally speaking, are meant to protect against engine breakdown by limiting friction, wear, heat, and deposits. Valvoline focuses on those factors in the formulation of its synthetic oil to offer a product that meets or exceeds the requirements of five different industry standards, including those set by ILSAC and the American Petroleum Institute. 

In addition, Valvoline lays claim to being America's first motor oil brand, having been founded in 1866 when Dr. John Ellis discovered that distilled crude oil made a good lubricant. Valvoline oil was later trademarked as the world's first petroleum-based lubricant in 1873.

Valvoline's synthetic motor oil lineup features formulations for a number of different applications, whether it's hybrid tech, European vehicles, cars with higher mileage, or even racing applications. The company's incredibly long history has led to an incredible amount of feedback on Amazon as well, with over 22,600 ratings and a 4.8 star average. At under $27 for a five-quart bottle of Advanced Full Synthetic, Valvoline manages to balance value, great engine protection, and a long history of reliability.

Castrol is a London-based company that got its start back in 1899 when it made the discovery that the addition of castor oil to lubricants designed for airplanes and automobiles thinned the mixture enough to allow it to work from cold starts while still maintaining viscosity at high operating temperatures.

Castrol's focus — at least in its marketing — is on making a motor oil that's designed primarily to fight the buildup of sludge in an engine. To that end, its GTX Full Synthetic is reportedly better at protecting against the buildup of sludge in engines when compared to the API's standard. In addition, GTX also provides wear protection six times better than that standard. Further, the Edge line of synthetics boasts the ability to maintain engine protection for 10,000 miles while also being a carbon-neutral product.

Amazon reviews for the product reveal a 4.8 star average, although only a little over 3,500 reviewers have left a rating -– far less than the last few entries on our rankings, but enough to show the loyalty from the Castrol crowd. That isn't limited to just customers, as Castrol Edge is the OEM partner of several of the world's largest automakers, including Honda, Volvo, Land Rover, Jaguar, Subaru, Ford, and Renault–Nissan–Mitsubishi.

In a choice that is likely unsurprising to most gearheads, Mobil 1 tops our rankings of popular synthetic oil brands. This best-selling product, made by the largest oil company in the world, ExxonMobil, has maintained a stellar name over years of performance in both motorsports and customer vehicles. The company's long history as a part of John Rockefeller's Standard Oil Company goes back over 140 years, and its name is synonymous with both gasoline and motor oil among hundreds of other products and industries.

Mobil 1 has a great reputation as the best motor oil available, with nearly every comparison video on YouTube pitting new competition against the established favorite. Its full synthetic formulation provides protection in extreme temperatures, minimizes timing chain wear, and protects engines for up to 10,000 miles between oil changes.

In fact, Mobil 1 is the number one best-selling motor oil on Amazon. 4.8 stars from nearly 37,000 ratings and page after page of positive reviews. A quick shopping search on Google reveals even more accolades, with 4.9 star review averages at retailers like Lowe's, Autozone, and Walmart.