Understanding Lubricant Base Oils

The simplest component of any lubricant is perhaps the base oil. However, it is also the most misunderstood. Unfortunately, some marketers use this misunderstanding to help promote their products with misleading information that is not necessarily false, but also is not completely true.

As explained in our short video https://www.youtube.com/watch?v=12Z-6UKSOYI there are five categories of lubricant base oils as defined by the American Petroleum Institute (API). The first two are comprised of petroleum base stocks that are refined to a relatively low standard. These base oils are normally promoted as petroleum based lubricants.

The third category of base oils is also petroleum based, but it is refined to a very high standard. These base stocks are promoted as full synthetic lubricants for reasons outlined in the above mentioned video.

The fourth category of base oils is comprised solely of polyalphaolefins. This is the entry level into the "true synthetic" base oil market. These base oils are comprised of molecules that are identical in size and shape. They have a much better ability to work over a wide temperature range and provide a very good viscosity index.

The fifth category of base oils is comprised of polyalkylene glycols, polyol esters, and di-esters. These true synthetic base oils have excellent oxidative and thermal stability, as well as an excellent viscosity index.

When searching for a synthetic motor oil, most consumers will be well served by the major brands even when the base stocks fall into the group three category of highly refined petroleum base stocks. For the average person who changes their oil in the 6-12 month time frame or every 5,000 miles, these motor oils will perform well. However, if you are driving your vehicle under more stressful conditions such as towing, racing, frequent idling or extended drain intervals, you may want to consider a motor oil with true synthetic base stocks.

Synthetic motor oils made from true synthetic base stocks will provide better fuel mileage, as well as lower evaporation loss and better resistance to thermal degradation.

Determining which brands of synthetic lubricants (motor oils or any other lubricant) are made from true synthetic base stocks can be very challenging. Unfortunately, most synthetic lubricants contain little if any true synthetic base stocks. It is best to review American Society of Testing & Materials (ASTM) test results to see how the motor oil or lubricant performs vs. the competition. Most reputable manufacturers will provide this information to help consumers make an informed decision. Synthetic lubricants and motor oils made from true synthetic base stocks generally outperform in these tests.