How Often Should You Get an Oil Change?

February 23, 2012

Learn about the oil plays in your engine, ideal oil change frequency, how conventional oil compares to synthetic oil, and oil change needs for hybrids.

Checking Oil

How often do you need to visit the shop for an oil change to keep it on the road for a long time? Here are some basic tips for knowing when you need to change your oil.

The Conventional 3000-Mile Change
With old-fashioned motor oils, mechanics recommend that a car owner change the oil every 3000 miles. Oil change shops will put a little sticker on your windshield that indicates when you should come back in, either at the next 3000 mile increment, or after a specific period of time. For synthetic oils, this number may change to 5000 or 7000 miles.

Shade Tree Wisdom
A shade tree mechanic is a family member or friend who routinely does their own repairs and maintenance and gives advice on auto maintenance. These individuals might give you a different story on oil changes. They may operate their vehicles much longer than 3000 miles before they change the oil and typically rely on two elements to tell them when the oil change is necessary. The first one is the color of the oil; as the oil gets used, it consistently becomes darker. When the original gold has faded to a dark brown or black, an oil change is in the cards. Second, they feel the oil for any sign of grit or buildup to know if it's time for an oil change.

Newer Vehicles
For those driving vehicles made in the 21st century, there's a new system for recommending oil changes. In many cases, the computer in your vehicle will tell you when it's time for an oil change. Many of these newer vehicles have digital readouts that signify how close the vehicle is to a recommended oil change. It is often significantly longer that the 3000 miles of the past.

Oil's Role in Your Engine
Oil plays a critical role in engine operation. Pumped through the engine under pressure, oil forms a thin film between all of the moving surfaces inside an engine, creating a physical boundary that prevents metal surfaces from touching. As time passes the oil becomes contaminated with byproducts of burning gasoline, reducing its effectiveness at providing that lubricating layer. The long chains of molecules that give oil its slick properties also are broken up due to the high pressures and forces inside an engine, reducing oil lubricity.

All this means that oil must be changed regularly to keep an engine running well. Changing the oil filter is also necessary at every service interval. The oil filter is responsible for removing particulates and other impurities that can damage the engine. Without clean oil, pistons can wear the engine block, decreasing power and economy, and allow oil to be burned in a blue smoky cloud. Cars that burn oil frequently fail emissions tests as oil can damage vehicle emissions equipment.

Dirty oil can also cause permanent engine damage. On engines that utilize timing chains, dirty oil can accelerate wear and cause a failed timing chain, which can potentially require an entire engine rebuild. Bearings can also wear prematurely, leading to engine seizure.

The most well known and most advertised reason to change motor oil frequently is sludge. Sludge is the infamous black goo that forms when compounds in the oil break down due to constant exposure to high temperatures and pressure. When the oil is oxidized, it separates and the additives sink and solidify. A certain amount of oil can only hold a limited quantity of contaminants. When the oil goes unchanged, excessive particles settle on the bottom, hence creating sludge. Sludge is a terrible problem to have with an engine because it can cause engines to seize up.

Using the Right Oil
Not only is it necessary to maintain clean oil in your engine, but it is also important to use the proper type and weight of engine oil. The two broadest categories of engine oil are synthetic and conventional oil. Conventional oil is derived from petroleum. It is refined from crude oil using distillation techniques. Modern conventional oils are far superior to those of years past, as techniques have improved and impurities have been reduced. Synthetic oils, while relying on the same basic chemicals for lubrication, are formed chemically from other compounds. This allows far greater control of oil quality and impurities.

Conventional Oil
Some conventional oils are marketed for higher-mileage vehicles (those with greater than 75,000 miles), but they do not necessarily need to be changed more often than other conventional oils. In fact, these oils (i.e. Pennzoil High Mileage Vehicle, Quaker State Higher Mileage Engine, Castrol GTX High Mileage) are usually marketed for their ability to help reduce minor oil leaks, not for altering the oil change interval. Also, many synthetic oils are not recommended for use in vintage or antique engines, which rely on some of the additional elements (such as zinc) within conventional oils to maintain proper operating performance.

Synthetic Oil
While synthetic oil is superior in terms of cleanliness and lubricating performance, it is not always necessary. Synthetic oil costs more and offers very little vehicle performance increase. In an average vehicle, synthetic oils are not necessary unless required by the manufacturer. Many vehicles running before widespread use of synthetic oils have been able to achieve in excess of 300,000 miles.

Synthetic motor oils (i.e. Mobil 1, Castrol Syntec, Quaker State Ultimate Durability, Pennzoil Platinum Full Synthetic) are sometimes recommended by vehicle manufacturers and auto mechanics. Although synthetic oils are generally more expensive, they usually provide a longer oil change interval than conventional oils. For example, some vehicle manufacturers advise an oil change interval of 7500 miles when synthetic oil is used; some others recommend an even longer interval.

Oil Viscosity
Engines are designed to operate with oil of a certain viscosity. Car manufacturers specify an acceptable range of oil viscosities, which are denoted by the numbers on the bottle. Almost all car oils are detergent oils that maintain their viscosity in many temperatures. Non-detergent oils should not be used without advanced engine knowledge.

Oil Change Requirements for Hybrid Vehicles
For the most part, hybrid vehicles should have their oil changed every 8,000 to 10,000 km, or roughly every 5,000 or 6,000 miles. However, you should check the owner's manual that came with your hybrid vehicle in order to make sure that you follow the guidelines established by the manufacturer.

Furthermore, some hybrid vehicles require a special type of motor oil that can add to the expense of performing an oil change. If you're not sure about which motor oil to use for your hybrid vehicle, you should visit the dealership where you purchased the car or thoroughly review your vehicles owners' manual.

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