Motor Oil Classifications
Motor oil classification systems and ratings are simply a way of establishing motor oil quality levels and appropriate applications for those oils. For automotive applications in the US, oils will generally be classified by their API rating, SAE viscosity rating, ILSAC rating and most likely by a number of more specific OEM (original equipment manufacturer - your vehicle or equipment manufacturer) motor oil ratings.
So, for instance, the 5w30 motor oil that you place in your vehicle has a 5w30 SAE viscosity rating, probably an SM or higher API rating, a GF-4 or higher ILSAC rating and possibly a number of other OEM specific ratings, such as from Ford or BMW, etc.
Are the Above Example Ratings Out of Date?
Well that depends upon when you are reading this. This FAQ document was written in November of 2007. As long as the automotive and lubricants industries continue to utilize API, SAE and ILSAC for motor oil ratings (which they have for YEARS and probably will for YEARS to come), the explanations in this FAQ will remain current. However, some of the specific ratings listed as examples may not be current.
For instance. Depending upon when you are reading this, the latest API rating may be "higher" than API SM or ILSAC ratings may have moved beyond GF-4. Don't let that "throw you off". The basic premise is still the same and the method of understanding these classification systems should still closely align with the explanations listed FAQ documents linked to below.
Originally, this FAQ document was intended to "contain" an explanation of all of the most widely used motor oil classification systems (API, ILSAC, SAE, etc.). However, as the article was being written, it became obvious that it should be broken into multiple documents discussing not only the classification systems, but also some of the other organizations involved in the process of classifying and certifying motor oils.
So, below you will find links to the various FAQ documents which detail each of the classification systems listed above as well as some other organizations that are involved in the overall process. Feel free to read any that interest you.
Motor Oil Classification Organizations
Check out this blog category to read about each of the various classification/certifying agencies related to motor oils & lubricants: Classification Organizations
Other Lubrication Aricles
There are numerous other informative articles on the site related to motor oils. Check them out in the following category: Motor Oil Tech Info & Articles