API Engine Oil Specifications Explained.

There are four major industry bodies that define engine oil specification by testing the lubricant based on specific crankcase application tests. Each one of them has their own test methods, criteria and parameters.

In this edition of OILY Academy, we will explain API engine oil classifications in more detail.


API (American Petroleum Institute) is the most commonly found classification standard on engine oil labels today. API puts the products submitted for licensing through numerous tests to determine the performance level of the lubricant.

After testing, API license that specific product according to performance level achieved, granting lubricant producer permission to print “API doughnut” on the product label. This enables the customer to select the tested lubricant correctly for the intended application. It should also be noted that not all lubricants will be certified by API, and many lubricants manufacturers will self-certify instead, meaning that they themselves guarantee product performance according to the mentioned specification.


The API approved products can be viewed here


API created two main categories of engine oil specifications:

1. Petrol engines

2. Diesel engine oils


The API specification for petrol engine oils


The specification for petrol engine oils can be identified by the letter “S” which stands for spark ignition.


The letter “S” will then be followed by a second letter, which designates the performance level. Together they constitute a specification, e.g. API SN.

The further along the second letter is in the alphabet, the higher is the performance level of that engine oil.



The API specification for diesel engine oils


Identified by the letter “C”, which stands for compression ignition.

The letter “C” will then be followed by a second letter which designates the performance level.

Just as before, both letters make up the specification of the oil. The “C’’ category may also include the numbers “2” or “4”, which further shows if the specification is for a two-stroke diesel engine or a four-stroke diesel engine, e.g. API CI-4.


All the latest diesel engines are, in fact, 4 stroke-cycle engines. The reason the stroke-cycles are indicated in the specification is to accommodate for some earlier construction equipment that runs with two-stroke-cycle diesel engines, but very little of them are still in operation.



When you’re unsure about which oil to purchase, please consult a qualified salesperson, or purchase the latest specification oil, because they are all backwards compatible.


Contact us for more information:

Email: info@oily.co.za

Phone: +27 021 410 8720


Click here to learn how to read an oil can label.


Written By Henco Booysen


#Genergy #Engineoil #Bestengineoil #OIYLYACADEMY #API #AmericanPetroleumInstitute #Automotiveengine #Petrolengine #Dieselengine #Car #Fsynth #AP I#ASCEA #ILSAC #OEMapprovals #Performacelevel #Viscosity #Carcare

32 views

© 2020 by Oily SA (Pty) Ltd.

7th Floor, Mandela Rhodes Place, Corner Wale Street and Burg Street, Cape Town, 8000

Phone: +27 021 4108720

  • Facebook - Black Circle
  • YouTube - Black Circle
  • Instagram - Black Circle