The In And Outs Of Engine Oil

AAA Auto Repair Article
By AAA Automotive
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Auto maintenance can be daunting, even when it comes to something as seemingly basic as motor oil. Based on the make and model of your vehicle, you need to consider the oil’s type, viscosity grade, service classification and whether it meets additional industry standards or proprietary specifications required by the manufacturer of your vehicle. Fortunately, you don’t have to be an expert to provide your automobile with the right oil. All it takes is your owner’s manual and an understanding of some easy-to-learn symbols and numbers printed on the engine oil packaging.

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Oil Types

Motor oil has come a long way since the late 19th century, when crude oil was first being refined into lubricants for the steam engines of that time. Contemporary offerings now include everything from conventional formulations to synthetic oils that offer superior performance. There are also oils designed to extend the lives of older engines in cars with many miles on the odometer. Here’s a quick primer on the most common oil types currently in use:

Conventional: Refined from crude oil and commonly recommended for older engines with simpler designs that are not expected to endure high-performance demands while driving. Conventional oil is typically less expensive, but generally requires more frequent changes.

Semi-Synthetic: A blend of conventional and synthetic oils (see below) that provides enhanced performance at a lower price point than a full-synthetic oil. Most late-model cars require semi-synthetic oil to meet automakers’ specifications.

Synthetic: Oils that are chemically engineered at the molecular level to reduce impurities, flow more easily at low temperatures and resist breakdown at high temperatures. Synthetic oils are more expensive, but offer the highest level of protection. The engines in many premium luxury cars and high-performance models require the use of synthetic oil.

High-Mileage: Designed for engines with 75,000-plus miles of use, high-mileage oils contain additives that help limit common problems such as oil leaks and increased oil consumption.

Oil Specifications

Oil type is important, but there’s more to know before topping up or changing the oil in your vehicle. Automakers and industry organizations have developed various oil standards, which appear on motor oil packaging in the form of two symbols called the “donut” and the “starburst”. The information provided by these symbols includes:

Society of Automotive Engineers (SAE) Viscosity Grade: The SAE viscosity grade—in the center section of the donut icon—refers to an oil’s weight or thickness, and indicates how easily it will flow to lubricate moving engine parts. Because outside temperature impacts viscosity, most modern vehicles call for multi-viscosity oils that perform well in a wide range of temperatures throughout the year.

American Petroleum Institute (API) Service Category: This code appears in the top half of the donut symbol and designates which API standard(s) the oil meets. The testing required to meet API standards involves a wide variety of requirements, from engine protection and performance to emissions control and compliance with government regulations.

Each category consists of a two-letter code, beginning with “S” for gasoline (spark) engines or “C” for diesel (compression) engines. The second letter denotes how current a standard the product meets, with “SN” and “CK-4” representing the most current standards as of January 2018.

In gasoline engines, you can use a newer service category of oil than that required by the vehicle manufacturer —for example, “SN” can be used in engines that call for “SM”. But, it is never okay to use oil with an older service category than that specified. The situation is more complicated with diesel engines, where the latest oil service category is not always compatible with earlier engine designs. Always follow the automaker’s recommendations for these engines.

International Lubrication Standard and Approval Committee (ILSAC) Standard: This rating for oil performance and engine protection is established by ILSAC, a standards organization made up of American and Japanese automakers. “GF-5” is the most current standard as of January 2018, and the presence of the starburst symbol on an oil package indicates compliance with the standard’s requirements for emissions control, seal compatibility, protection of turbochargers and pistons against high-temperature deposit formation and more.

Automaker and Diesel Engine Manufacturer Standards: In addition to the industry standards described above, most automakers and diesel engine manufacturers have proprietary motor oil standards designed around the unique needs of their powerplants. The standards are identified by alpha-numeric codes that appear in owners’ manual and on the packaging of oils that meet the necessary requirements.

Protect Your Engine

Your engine is the heart and soul of your automobile, and using the right type of oil is essential to both its performance and longevity. When selecting motor oil to service your car, always refer to the owner’s manual to determine the specific requirements of your particular vehicle.

For greater peace of mind throughout your travels, consider Roadside Assistance by AAA. With trusted round-the-clock service, you’re covered virtually anytime, anywhere, no matter what you drive.
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