Automotive Lubricants

Many types of lubricants are used in a vehicle. Engine oil and transmission fluid, on a volume basis, provide a major portion of the lubricants in a typical car or truck, and a great number of standard tests and specifications like API, ACEA, SAE, JASO, NLGI and other country specific specifications are associated with these fluids.

Greases provide a variety of highly specialized functions and are found in many locations within a vehicle (for example, indoor locks, gears for seat adjustments and windshield wipers, bearings, electrical contacts, and numerous other places). In general, automotive lubricants consist of a base stock and various additives. The choice of base stock depends on the function of the lubricant. In the case of engine oil, various types of organic oils may be used: paraffinic, naphthenic and synthetic. Paraffinic hydrocarbons consist of hydrogen and carbon atoms that are chemically bonded together in the form of branched chains. Naphthenic hydrocarbons contain carbon atoms that are bonded together in the form of rings. Paraffinic and naphthenic hydrocarbons are typically derived by refining oil from oil wells. Synthetic hydro carbons are formed by combining small hydro carbon building blocks to form longer chains of a desired composition that tends to be more resistant to chemical attack than is the case for oils produced by a refining process.

Additives are blended into a base stock to provide desirable properties such as optimum friction characteristics for the desired application, anti-wear and antioxidant capability, defoaming capability, and corrosion inhibition. The chemical nature of the additives for a given application are chosen on the basis of their ability to perform their desired function, withstand the conditions under which they must operate and be compatible with the base stock in which they are used.

Automotive lubricants can be broadly classified into as per the applications and uses. commercial vehicle Engine lubricants (For use as engine lubricant in trucks, trailers, dumper etc) Service vehicle engine lubricants (For use as engine lubricants in cars , jeeps ,SUV’s MAV etc),Two/Three Wheeler Engine Lubricants (Two Stroke/Four Stroke) Gear, Axle and Transmission Lubricants for any type of vehicle.


Oil is defined as a liquid lubricant used to reduce friction between moving parts. This reduction of friction is what allows your engine to work correctly. As oil breaks down it is not able to do its job well and that is why oil changes are needed. With that basic knowledge regarding oil we will move on to the industry set that provides the rating systems. The groups that standardized the oil rating system are the Society of Automotive Engineers (SAE), the American Society for Testing and Materials (ASTM) and the American Petroleum Institute (API). These three entities collaborated to provide the rating system as it is today. Now that you have some simple information on oil itself and the industry groups that created the ratings system. Let’s take a look at the actual rating system used for oil. There are two types of ratings to be familiar with when discussing engine oil. These types are service requirement (or quality) and viscosity requirement.

In the 1940s the service ratings were classified as Regular, Premium or Heavy Duty. In the 1950s these classifications were replaced with ML, MM and MS the order was to show the increasing quality of the oil. Finally in the 1980s there was another revision of the service ratings that continues to be used in present day.

The current service ratings came about by testing done by the American Petroleum Institute (API). The service ratings classification system starts with SA and proceeds to SM currently. According to the API’s motor oil guide SM, SL & SJ are the current rating levels that are being used for gasoline powered vehicles. Ratings below SJ are considered obsolete which means they are for older vehicles. API recommends motorists refer to their owner’s manual before deciding which service rating is correct for their vehicle.

The second oil rating system is designated as viscosity. The viscosity rating will be the number printed on the motor oil container that starts out SAE. SAE is the group that classifies the viscosity type after testing the oil at different temperatures. There are different grades of viscosity that have been defined. Six of these grades end in the letter W, with the W standing for winter. These six levels start with 0W and continue up in steps of 5 ending with 25W. The remaining five grades start at 20 and proceed to 60 in steps of 10. The higher the number the higher the viscosity level is the general rule. The viscosity level measures the oil’s thickness and ability to flow at certain temperatures. The purpose of having a viscosity rating for engine oil is to assure that whatever temperature the vehicle’s engine is operating at that the oil will be able to flow smoothly through the whole lubrication system. At high temperatures oil tends to thin out while at low temperatures oil can get too thick. That is why there are two types of viscosity ratings: single and multi-viscosity.

Single viscosity oil varies in thickness for wide variety of temperatures or climates. You can spot single viscosity oil by it only having one number, such as SAE 40. This single number is due to that fact that oil is a simple, straight grade of petroleum. Multi-viscosity oil slowly changes in viscosity as the temperature changes. Multi-viscosity oil has been designated to have two numbers such as SAE 15W-40. The double number refers to the oil behaving in two ways. It will act like a conventional 15W oil would at 0 degrees Fahrenheit and like a conventional 40W oil would at 200 degrees Fahrenheit. The advantage to consumers using multi-viscosity oil is that it can sustain ample thickness at high engine temperatures while it withstands the tendency to thicken at very low temperatures.

The oil rating system is made up of two parts, the service rating and the viscosity grade. Both ratings systems are continually being tested and revised as new information and technology come to light. The best way to insure you are buying the proper engine oil for your car is to consult the owner’s manual that came with your vehicle.As a side note the API has a different guide for diesel powered engines. This classification system goes from CA to CJ-4. CJ-4 was introduced in 2006 for high speed 4-stroke engines. A good tip on remembering which rating system is for which type of oil is that S = spark ignition while C = compression ignition. The API also gives oils an “Energy Conserving” rating if the oil meets certain criteria for reducing friction and oil consumption, and improving fuel economy.