Car maintenance can be intimidating, even when it comes to something as basic as engine oil. Depending on your vehicle’s make and model, you need to consider the oil type, viscosity grade, service classification, and compliance with additional industry standards or specific requirements from your vehicle manufacturer. Fortunately, you don’t need 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.
Oil Types
Engine oil has come a long way since the late 19th century, when crude oil was first refined into lubricants for the steam engines of the time. Contemporary offerings now include everything from conventional formulations to synthetic oils that offer superior performance. There are also oils designed to extend the life of older engines in cars with high mileage. Here is a quick introduction to the most common types of oil currently used:
• Conventional: Refined from crude oil and generally recommended for older engines with simpler designs that are not expected to handle high-performance driving demands. Conventional oil is typically cheaper but usually requires more frequent changes.
• Semi-Synthetic: A blend of conventional and synthetic oils (see below) that offers improved performance at a lower cost than fully synthetic oil. Most recent car models require semi-synthetic oil to meet automaker specifications.
• Synthetic: Oils that are chemically modified at the molecular level to reduce impurities, flow more easily at low temperatures, and resist degradation at high temperatures. Synthetic oils are more expensive but offer the highest level of protection. Engines in many high-end luxury cars and high-performance models require the use of synthetic oil.
• High Mileage: Designed for engines with over 75,000 miles of use, high mileage oils contain additives that help limit common issues such as oil leaks and increased oil consumption.
Oil Specifications
The type of oil is important, but there is more to know before topping off or changing your vehicle’s oil. Automakers and industry organizations have developed various oil standards, which appear on engine oil packaging in the form of two symbols called the “donut” and the “star.” The information provided by these symbols includes:
• SAE (Society of Automotive Engineers) Viscosity Grade: The SAE viscosity grade (in the center of the donut icon) refers to the weight or thickness of an oil and indicates how easily it will flow to lubricate the engine’s moving parts. Since outside temperature impacts viscosity, most modern vehicles require multi-viscosity oils that perform well across a wide range of temperatures throughout the year.
• API (American Petroleum Institute) Service Category: This code appears in the top half of the donut symbol and designates the API standard(s) the oil meets. The tests required to meet API standards involve a wide variety of requirements, from engine protection and performance to emission control and compliance with government regulations.
Each category consists of a two-letter code, starting with “S” for gasoline (spark-ignition) engines or “C” for diesel (compression-ignition) engines. The second letter indicates how well the product conforms to a current standard, with “SN” and “CK-4” representing the latest standards as of January 2018.
In gasoline engines, you can use a service category oil that is newer than what the vehicle manufacturer requires—for example, “SN” can be used in engines that call for “SM.” However, it is never acceptable to use oil with an older service category than 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.
• ILSAC (International Lubricant Standardization and Approval Committee) Standard: This oil performance and engine protection rating is established by ILSAC, a standards body composed of American and Japanese automakers. “GF-5” is the latest standard as of January 2018, and the presence of the star symbol on an oil package indicates compliance with the standard’s requirements for emission control, seal compatibility, protection of turbochargers and pistons from high-temperature deposit formation, and more.
• Automaker and Diesel Engine Manufacturer Standards: In addition to the industry standards outlined above, most automakers and diesel engine manufacturers have exclusive engine oil standards designed around the unique needs of their powertrains. The standards are identified by alphanumeric codes that appear in the owner’s 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 for both its performance and longevity. When selecting engine oil for your car’s maintenance, always refer to the owner’s manual to determine the specific requirements for your particular vehicle.
