Engine Oil Basics: SAE Ratings, Viscosity, Additives, and More

Reviewed by

Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at CarParts.com

Written by CarParts.com Research Team - Updated on December 17th, 2024

Reading Time: 5 minutes
Summary
  • SAE stands for “Society of Automotive Engineers.” It’s the governing body that dictates the engine oil’s grade number, indicating its viscosity range.
  • The International Lubricant Standardization and Approval Committee (ILSAC) rating is represented by a starburst symbol on motor oils. It consolidates the SAE viscosity and API quality rating.
  • The four types of engine oil are conventional, synthetic, synthetic blend, and high-mileage oil.

Following your vehicle’s preventive maintenance schedule (PMS) is key to keeping your daily driver around for a long time. And getting a periodic oil change is one of the many tasks you should stay on top of. 

The type of oil you’re putting into your engine is as important as sticking to other maintenance tasks. Using the wrong oil can result in several complications and eventually damage your engine, so you must know how to pick the right one. 

Read on to find out the basics of engine oil and the things you should look out for when it’s time to buy some. 

SAE and API Ratings

The American Petroleum Institute (API) program certifies that an oil meets certain Original Equipment Manufacturer (OEM) quality and performance standards. The service rating is shown in the API “Service Symbol Donut” on the product label. The “S” classification on the API is for “Spark Fired” (gasoline) engines and a C classification is for “Compression” Fired engines (diesel). The “Starburst” is another API seal that can be used to identify oils which meet the latest International Lubricant Specification Advisory Committee (ILSAC) standard, currently designated ILSAC GF-6A. | Image Source: Richard McCuistian

Getting the right SAE rating or grade number of engine oil is crucial to maintaining your vehicle’s exceptional performance. But what exactly does SAE stand for?

SAE stands for “Society of Automotive Engineers.” It’s the governing body that dictates the engine oil’s grade number, indicating its viscosity range. 

For example, if the engine oil has a rating of SAE 30, it means that the oil has been checked at 212℉. If the engine oil has a “W” at the end of the grade number, it means that it was tested at 0℉ and is suitable for winter conditions.  The “W” stands for “Winter,” not “Weight.”

Viscosity refers to the engine oil’s thickness and capacity to flow under certain temperatures. Engine oils with a high viscosity index thin less with heat than those with a low viscosity index.

A Closer Look at the SAE

The Society of Automotive Engineers was inaugurated in 1905 with Andrew Riker serving as the organization’s first president and Henry Ford as the vice president.

The SAE is a global association of over 128,000 engineers and technical experts from various industries, including aerospace, automotive, and commercial vehicles. 

It was created with the need to provide a space for engineers in the automobile business to exchange ideas and expand their technical knowledge base.

ILSAC Rating

Getting the right SAE rating or grade number of engine oil is crucial to maintaining your vehicle’s exceptional performance.

The International Lubricant Standardization and Approval Committee (ILSAC) rating is represented by a starburst symbol on motor oils. It consolidates the SAE viscosity and API quality rating.

Engine oil with the ILSAC rating is suitable for use in almost any gasoline engine.

Engine Oil Additives

Many manufacturers produce oil with additives that help improve the base oil and protect the engine. Here are some of the most common additives you’ll find in engine oils:

  • Viscosity index improver
  • Pour point depressant
  • Antifoam agents
  • Oxidants and antioxidants
  • Total base number
  • Rust and corrosion inhibitors
  • Antiwear additives
  • Extreme pressure additives

Types of Engine Oil

There are four types of engine oil: conventional, synthetic, synthetic blend, and high-mileage oil.

Conventional Motor Oil

Conventional motor oil is refined crude oil that’s typically used in new, light-duty vehicles that have a simple engine design.

Synthetic Motor Oil

Synthetic motor oil costs twice as much as conventional motor oil because it undergoes a series of refining processes. Synthetics tend to remain fluid at very low temperatures, making them a popular choice for drivers living in colder climates.

Synthetic Blend Motor Oil

Synthetic blend motor oils combine synthetic oil with conventional engine oil. It’s a cost-effective alternative for drivers who want a better motor oil variant in their engines than conventional oil.

High-Mileage Motor Oil

High-mileage motor oil is ideal for engines that have over 75,000 miles. It contains esters that swell the oil seal and lack the energy rating of conventional oils. A lot of high-mileage oils lack friction-reducing additives, which means they can’t meet the ILSAC GF-4 rating.

Importance of Getting an Oil Change

Besides lubricating engine parts, engine oil also performs the following functions:

  • Cool engine parts
  • Seal piston rings
  • Neutralize acids produced during the combustion process
  • Reduce friction between moving parts
  • Prevent rust and corrosion

Oil Change Intervals

The recommended oil change interval for vehicles is usually indicated in the owner’s manual.

The recommended oil change interval for vehicles is usually indicated in the owner’s manual. Most vehicle manufacturers suggest getting an oil change anywhere between 7,500 and 12,000 miles (between 12,000 and 19,000 kilometers).

However, some conditions could affect this interval, such as:

  • Driving in dusty areas
  • Towing a trailer
  • Operating below-freezing temperatures or in cold weather
  • Frequently operating at extended idle speeds

If one or more of the conditions are present, vehicle manufacturers recommend getting an oil change anywhere between 2,000 and 3,000 miles.

Some vehicles also come with oil life monitors. These monitors trigger a warning light on the dashboard to alert the driver when the vehicle is due for an oil change.

These oil change monitoring systems can either be a mileage-only or algorithm-type system. A mileage-only monitoring system relies on mileage information, while an algorithm-type system uses information like the number of cold starts, engine run time, and engine coolant temperature (ECT) sensor input.

Engine Oil Brand Compatibility

You’ll find dozens of engine oils stamped with different brands in the market, and you might even hear some drivers and experts recommending certain ones. But does the brand really matter?

According to the SAE standard J-357, all engine oils must be compatible with all other brands of engine oil. This refers to the engine oil’s property called “miscibility,” which means it’s capable of mixing with other oils without causing any problems like sludge.

Following the SAE standard J-357, any brand of engine oil can be used as long as it meets the viscosity and API standards set by the vehicle manufacturer.

Where to Get Quality Engine Oil for Your Vehicle

Getting the right type of engine oil is very important if you want to keep your vehicle running smoothly. Routine oil changes will help prevent engine sludge and other nasty problems. When choosing where to buy your oil, it’s important to find a place you can trust. Thankfully, CarParts.com has you covered on that front.

CarParts.com has a wide range of engine oils for you to choose from. All you need to do is pick the one that best suits your vehicle according to its owners manual and the points in this guide. From there, it takes only a few quick clicks to take your items through our convenient and secure online checkout. If you plan to do an oil change soon, you can rely on our fast shipping. We’ll have your new engine oil shipped to your door in as fast as two business days.

Order your new batch of engine oil at CarParts.com today.

About The Authors
Reviewed By Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at CarParts.com

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Written By CarParts.com Research Team

Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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Published by
CarParts.com Research Team and Richard McCuistian, ASE Certified Master Automobile Technician
Tags: motor-oil