There are no definitive guidelines on what should be considered high mileage. With the technology available today, standard road vehicles can last up to , miles or even , miles. It is commonly understood that highway miles are less taxing on an engine than city miles, and research seems to support this. Highway miles have fewer starts and stops. The engine can also reach a steady temperature and operate at peak efficiency for a long period of time.
City driving is just the opposite. So, an engine with 80, miles may have as much wear as an engine with , miles. It all depends on how the vehicle has been driven and maintained.
Some people might consider switching to a high mileage oil at , miles, while others may want to change to a high mileage oil at 80, miles. For the average driver, anything over , miles could safely be considered a high mileage vehicle. Since most additive packages appear to be quite similar, it can be difficult to distinguish any real differences between many engine oils.
The concentration of additives most likely is the primary distinction. Motor oil formulations are treated as trade secrets, so obtaining specific additive amounts and quantities can be nearly impossible. Safety data sheets typically only identify a range of additive percentages, and all the additives may not even be included if they are inert. Most of these additives are intended to minimize the asperities on metal surfaces by filling those microscopic valleys and creating smoother mechanical surfaces.
Several studies have shown promise with this approach, but more research is still needed to determine the best way to stabilize these nanoparticles in oil suspensions. While this appears to be a straightforward question, more than one answer may apply. Depending on what you read or whom you listen to, you might receive conflicting advice. To say that either side is right or wrong would be a fallacy.
An engine that has been well cared for , with all the scheduled maintenance performed, should be able to support longer intervals between oil changes. As an engine is broken in, the sharp little edges and rough surfaces become polished down, enabling the surfaces to mate better and lessening the chances of metal-to-metal contact assuming full-fluid separation at the operating temperature. A caveat to this would be when there is wear in the cylinders and on the rings, which may allow blowby.
If you know what you are looking for, a comprehensive oil analysis test slate may not be necessary. A simple blotter spot test may be enough to determine if you have fuel dilution or coolant in your motor oil. To help you decide if your high mileage oil change intervals can be longer, consider the following advice:. If your engine burns oil or you must add oil to it at regular intervals, you should not try to extend your oil change.
If you have performed a compression test on your engine and found that you are losing pressure, you should avoid extended oil change intervals. If you are not using a quality filter, you should not extend your oil change. Reconsider the filter you are using, as it will have the greatest impact on engine life.
The better the oil is filtered, the longer the engine and oil will last. If switching from a conventional mineral oil to a synthetic oil, you may have issues with leakage depending on the synthetic used and the types of seals in the engine.
This could be caused by seal incompatibility or residue buildup being cleaned out of areas where it was previously sealing a leak. Synthetic oils have advanced over the years, and motor oil manufacturers are taking this into consideration, so this issue is becoming less of a problem. As fuel-economy standards change and new technologies and engine metallurgy are introduced, the classifications for engine oils must also change.
With this in mind, it is important to read the labels on the oils you buy for your vehicles. For four-stroke road vehicles running on diesel engine oil, the most current category is CK For low-sulfur diesel engines manufactured in or later, you may need an engine oil classified as FA This classification indicates that these oils have been specifically formulated to reduce greenhouse gas GHG emissions.
These new motor oil classifications are backward compatible, so using a newer category oil on an older vehicle should not create any issues. Detergents, just as they do when washing your laundry, prevent contaminants from depositing on the interior surfaces of the engine. The problem is that the best such ingredient is phosphorus.
Maybe these secret ingredients are the same ones in the anti-wrinkle creams some of us use to fight the human effects of aging! In the old days, drivers would simply switch to a much thicker motor oil to help bridge the large gaps inside worn engines to minimize how much oil slips past piston rings and gets burned in the combustion chamber.
However, modern engines are no place for old-fashioned weight oil. Drivers should always use the oil specified by the manufacturer, advises Smith, even though that is often watery-looking 0W When steel oxidizes you get rust, so we have anti-rust components to combat that. Even the oil can suffer the petroleum equivalent of rust, he added. It thickens up, so we have antioxidants to combat that so the oil will stay fresh and do its job.
The engineered hydrocarbons in synthetic oil are more resistant to breakdown than natural oil is, helping the oil preserve its intended characteristics between oil changes.
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A member of the North American Car of the Year jury, Dan is Popular Science magazine's automotive editor, writing car reviews as well as auto industry analysis and commentary.
He specializes in analyzing technical developments, particularly in the areas of motorsports, efficiency and safety.
Effective May 25, , our Privacy Policy has changed. You must agree to the new Privacy Policy to continue to use Team Valvoline. Agree 0. High-mileage oils have ingredients to take care of older engines, like conditioners, seal swells, antioxidants, detergents and wear or friction additives.
These oils need to stay thicker longer to protect engine parts. Over time, anything mechanical—even door handles—begins to loosen. Seals, gaskets and non-metal parts begin to decay as an engine ages. The higher-mileage oils are formulated with seal conditioners that increase flexibility and restore shape, which can help prevent leaks in the long run.
The bottom line is that high-mileage engine oils are designed for engines that are beyond their warranties and have , , , miles.
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