Is synthetic oil better than high mileage oil

Synthetic oil, once found mostly in high-performance cars, is being used in more mainstream vehicles.

Take, for example, the popular Honda Civic. A Honda spokeswoman said the automaker uses a synthetic oil in the Civic for its low viscosity—meaning it flows more easily than oils with higher viscosity—which helps to improve the engine's fuel efficiency. The faster the oil flows, the quicker the engine parts can turn.

Honda is not alone, says Mel Yu, auto analyst at Consumer Reports. In the 2019 model year, about 70 percent of new cars get either fully synthetic or blended oil.

Several brands, including Honda, don't specifically require synthetics for their engines, but the low-viscosity oils that those engines need are offered only in a synthetic format, Yu says. Some brands use “synthetic blend” oil, which is a combination of conventional and synthetic oils. Blends don’t deliver the full benefits of synthetic, but they’re considerably cheaper, he adds.

On top of that, many oil-change outlets also offer synthetic oil as an alternative to conventional engine oil.

According to Will Hixson, spokesman for the Automotive Oil Change Association, the 2018 National Oil and Lube News annual survey shows that more than half of car owners are choosing synthetics or synthetic blends when they get their oil changed.

Should you use synthetic oil? There are good reasons to—but only if your car has specific needs.

Synthetics have some advantages over conventional motor oil. They’re designed to be more effective at:

• Resisting oil breakdown, which makes it last longer than conventional oil
• Withstanding higher temperatures than conventional oil, which helps keep engines running longer
• Flowing in cold temperatures, thus reducing engine wear during frigid startups.

There's a downside: Synthetic motor oil can cost two to four times as much as regular oil. So unless your owner's manual specifies synthetic, you don’t need it.

But John Ibbotson, Consumer Reports’ chief mechanic, says there are some situations where synthetic oil’s resistance to breakdown (the tendency of oil to degrade and lose its viscosity over time) can help prolong the life of an engine:

• If you make lots of short trips, standard motor oil may never get warm enough to burn off moisture and impurities that can accumulate. That could hasten the breakdown of conventional oil.
• If you live in a region with very cold winters or very hot summers, or if you use your vehicle for towing or hauling heavy material, synthetic oil helps protect the engine from strain and won’t break down as quickly as conventional oil.
• If you have an older engine that’s prone to sludge buildup. This gunky residue forms when oil breaks down, and it can block oil passages and lead to a quick engine death. In the early 2000s, several engines from Chrysler, Toyota, and Volkswagen, among others, were especially prone to sludge buildup. Synthetic oil is less likely to form this troublesome sludge.

Though synthetics generally hold up better for more miles, regular oil changes remain important, and you shouldn’t wait beyond the time interval recommended by the manufacturer—typically every six months or a year.

Using synthetic in these situations will prolong your oil life and require fewer changes. That’s also a major benefit to the environment, as used motor oil is a major source of toxic waste in water.

Patrick Olsen

I've been a journalist for decades, and I got my love of cars from growing up in Los Angeles, where you have to drive, even if you're just going a few doors down the block. I'm a huge movie, music, and TV fan, and really just a devotee of good storytelling. 

Top 5 synthetic motor oil FAQs

Is synthetic oil better than conventional oil? Should I consider changing from conventional oil to synthetic oil? What’s the real difference between full synthetic, synthetic blend and conventional oil? Find the answers to the most frequently asked questions here.

5. Is synthetic oil better for my engine than conventional oil?

Yes, synthetic oil is better for your engine than conventional oil. Although conventional oil (i.e., mineral oil) can provide adequate lubrication performance, it can’t compete with the overall engine performance and protection provided by synthetics.

Synthetics use higher quality base oils as compared to the less-refined base oils used in conventional oils which makes conventional oils:

• Less chemically stable
• Oxidize and acidify more easily
• Quicker to break down and lose protective qualities

Overall, full synthetic oils provide better engine performance and protection than conventional and synthetic blend motor oils. Mobil 1™ advanced full synthetic motor oils are specially formulated with a tailored additive system that provides additional performance benefits above and beyond those found with conventional and synthetic blend oils by:

• Combating sludge and deposit buildup
• Reducing wear
• Protecting against high temperatures
• Controlling oil breakdown

So all of the chemistry that starts in a lab really makes a big difference on the road.

4. What are the advantages of synthetic oil over conventional oil?

Synthetic oils are created through complex processes, including being chemically developed from petrochemicals, to have the exact molecular qualities needed for a specific application.

These processes remove impurities from the crude oil and enable individual molecules to be tailored to the demands of modern engines. These customized molecules in synthetic oils provide higher levels of performance and protection than conventional oils.

So how do synthetic oils outperform conventional oils?

• By offering greater engine wear protection

  Engine parts are in constant contact with each other and moving at high speeds. In the extreme environment of your engine, components can wear and break down. Your motor oil is the only protective barrier between these components.

  As conventional and synthetic blend oils break down, typically, their ability to prevent engine wear diminishes. But Mobil 1 full synthetic oils retain their wear protection properties for a much longer time, helping to increase engine life by keeping important engine parts in excellent condition for 250,000 miles.*

  *Total engine miles. Tested in vehicles primarily in city and highway driving conditions with respective product recommended oil change intervals.

• By keeping your engine cleaner

  As oil circulates through your engine, it can pick up deposits. Over time, conventional oils can form sludge, which can reduce your engine's efficiency and, ultimately, reduce the life of your engine. Mobil 1 full synthetic oils contain fewer impurities compared to conventional and synthetic blend oils and can better resist the formation of sludge and deposits in your engine. If your engine already has sludge, Mobil 1 motor oils clean up virtually all engine sludge in just one oil change.

• By flowing better in low temperatures

  When your vehicle is not being driven, the oil settles. But when you fire up the ignition, it begins flowing through critical engine parts to protect against friction. Conventional and synthetic blend oils take more time until they are able to flow smoothly through the engine. During cold winter months, or if you live in an extremely cold environment, this flow process takes even longer. Mobil 1 full synthetic oils are engineered to flow quickly even at low temperatures, and they start protecting your engine right after you start your vehicle.

• By protecting better at high temperatures

  When running, engines are hot. Over time, the high temperatures in your engine can cause conventional and synthetic blend oils to break down or evaporate, exposing your engine to wear. Mobil 1 full synthetic oils are engineered to resist these high temperatures, which is especially important if you’re driving in hot climates or requiring your engine to work harder such as while towing or hauling.

• By protecting critical turbocharger parts

  Automakers are building cars with smaller engines (for greater fuel efficiency) and turbochargers (to boost power). Turbocharged engines run even hotter than non-turbo engines. Oil in a turbocharger can exceed 400° Fahrenheit and the shaft inside a turbocharger can spin upwards of 200,000 revolutions per minute, so it’s important that motor oil flows quickly to these critical parts for proper lubrication.

  Conventional and synthetic blend oils can break down faster under extreme turbo conditions and leave deposits on turbocharger components, which can lead to failure. Mobil 1 full synthetic oils can protect these components much better than conventional oils, keeping them operating at peak performance and boosting engine power. conventional oils, keeping them operating at peak performance and boosting your engine’s power.

3. Does synthetic oil have longer oil change intervals than conventional oil?

Yes, generally, synthetic oil can provide longer oil change intervals than conventional oil. But this is often dependent upon the brand of motor oil and several other factors, such as driving style and driving conditions. Please follow the recommendations in your owner's manual while your vehicle is under warranty.

Some synthetic motor oil brands still recommend oil changes every 3,000 or 5,000 miles. The Mobil 1 lineup includes full synthetic motor oils that support oil change intervals ranging from 7,500 miles, to 20,000 miles or one full year .†

†Whichever comes first.

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

While there are no firm industry definitions, full synthetic motor oils typically use the highest quality base oil combination as a starting point. Synthetic blend motor oils will typically be either a blend of high-quality and lower-quality conventional base oils or all high-quality (higher than conventional) base oils. But the synthetic base oil is only half the story. The correct blend of additives must go into the mix to create the oil.

The tailored additive system in Mobil 1 full synthetic oils gives the additional performance benefits above and beyond those found with synthetic blend oils. And while full synthetics as a motor oil category provide better protection than conventional and synthetic blend oils, not all synthetics are created equal.

1. My car doesn’t require synthetic motor oil. Can I change from conventional motor oil to full synthetic motor oil?

Switching from conventional motor oil to full synthetic motor oil is perfectly acceptable. Mobil 1 full synthetic motor oils are compatible with conventional oils, oils for high mileage vehicles, synthetic blends and other full synthetic oils. Engine flushing is not required.

For high mileage engines

However, if your vehicle has a high mileage engine (e.g., engine with more than 75,000 miles) that has never used synthetic motor oil, or one that has been poorly maintained with infrequent oil changes, we recommend easing into extended oil change intervals to allow Mobil 1 oil to clean up the engine. In these cases you should still follow the same basic oil change procedures (drain the old oil, remove the old oil filter, put in new Mobil 1 oil and put on a new oil filter).

Follow your OEM’s recommended maintenance practices regarding oil changes, but you should follow more frequent (one or two non-extended drain) oil changes when first switching to synthetic oil. The reasoning behind these shortened oil change intervals is that a high mileage engine, or one that has had a lack of maintenance (including infrequent oil changes), will likely have a considerable buildup of sludge and deposits.

Mobil 1 oil will help clean the engine as you drive, but it will have to work much harder in a very “dirty” engine and so it is best to change the oil more frequently for those first several thousand miles. After that, you can rest assured that Mobil 1 oil is continuing to keep your engine running clean and well lubricated for mile after mile.

A quick word from eHow’s Auto Center

Synthetic? Conventional? Hear automotive expert Chris Duke share his knowledge on the topic.

Is synthetic oil better for high mileage cars?

Is high mileage oil and synthetic oil the same?

What are the disadvantages of synthetic oil?

Can you switch to synthetic oil with high mileage?