Basics of the Bike Engine Oil

There are a number of traits which both the human beings and machines share in common. Being a machine, motorcycles too need a medium through which they can operate in their best standards and up to their credentials. Just as the blood acts a flowing lease of life for us humans, the engine oil, or lubricant as they say, is thoroughly responsible for the smooth and trouble-free operation of the engine of a motorcycle. The longevity, overall performance, efficiency, NVH levels and life depends a lot on the engine oils. There are several characteristics which these engine oils come along with. Let’s cover up them one-by-one:-

WHAT ACTUALLY THE ENGINE OIL IS?

Call it, whatever you want it. In a layman’s words, the engine lubricant, or engine oil as it is most commonly known as, is a liquefied substance which has an oily character to it. In effect, it is that oil, which is commonly used for better performance and smooth operation as it lubricates the internal parts and components of the engines of the motorcycles. The primary objective of this particular oil is to reduce the friction between the parts of an engine which are in motion and thereby increasing the life by reducing the wear. Apart from this aim, thanks to its sticky and flowing nature, it also cleans the dirt, dust or any other alien particles which get clogged on the internal surface and boundaries of the engine. It increases the probability of the engine’s better performance and prolonged life by avoiding the corrosion, as it keeps the internal surface of the engine always in a wet state. Lastly, it also keeps the soul of the engine ‘cool’ by keeping the temperature of the engine as low as possible, but in a satisfactorily operating condition, by absorbing all the dissipated heat generated by the movable parts of the engine.

Basically, being a semi-solid or a liquid in nature, the engine lubricants for motorcycles are derived from chemical compounds, which are based on petroleum or non-petroleum synthesized products. Nowadays, the motor oils being used are mainly made up by blending a hydrocarbon base oil and various chemical olefins, which generally comprise of carbon and hydrogen as the main constituents. The base oil may contain esters up to 25% for aided performance at peak power conditions of the motorcycle engines.

WHAT ARE ITS USES?

The basic objective of adding the engine oil or lubricant is not a hidden science. The motor oil/lubricant for motorcycles performs the same operations and functions as they do in other machines and engines. Scientifically speaking, inside an internal combustion engine of a motorcycle which runs on a fossil fuel like petrol or diesel, there are several small or big components, which are in motion with respect to each other. The motion between them generates a lot of frictional energy which is nothing but the heat generated from the kinetic energy of the moving components. This friction, generated repeatedly, wears up the mechanical components within a particular period of time, which may lead to depreciation in the efficiency, performance and life of the engine, ultimately resulting in lower power output and fuel consumption than the desired ones.

It is in this place, where the engine lubricant comes in action. This engine oil acts as a savior by creating a very thin film, which separates the surfaces of the two components moving adjacent to each other. This film avoids the direct contact between these two components by a fair margin, which finally results in decrease in the amount of heat produced due to friction, thus increasing the protection factor of the engine.

The ever-flowing action of the lubricant also keeps the internal components of the engine coated with the lubricant, thus acting as a layer between the surface of the component and atmospheric oxygen, thus preventing corrosion or formation of rust even at higher temperatures. In addition, many engine lubricants come with detergents as well, which when being flowing with the oil, keeps on cleaning the engine and keeps it free from the formation of any kind of oil sludge, by trapping the soot formed from the combustion of fuel in itself.

Apart from all these prime objectives, as an additional serve, the engine lubricant also acts as a coolant by keeping the engine temperature in control under high load conditions by its flowing action. Usually, in the petrol-operated engine of a motorcycle, due to the repetitive to and fro motion of the piston inside the cylinder, the top piston ring causes the engine oil temperature to expose to temperatures as high as 160°C. At such elevated temperature conditions, the engine lubricant with a higher viscosity index proves to be beneficial.

WHAT ARE ITS PROPERTIES?:-

Performing so many multi-functional tasks needs a lot of strengths and attributes, and the engine lubricants have a series of them. The motor oils for motorcycles generally consist of hydrocarbons which have 18 to 34 carbon atoms per molecules. Such high affinity of carbon results in the better withstanding actions, which are desired from the engine oil.

The first and the most important property to be looked upon in the engine lubricant is the viscosity, which is basically the thickness of the flow of the oil, or the resistance measured to the flow. For a proper lubricating thin film between the moving adjacent engine components, the engine oil must have suitably high viscosity, so that it may also flow around the components of the engine. The viscosity of this engine lubricant is defined by its viscosity index, which tells that what will be the change in the viscosity of the oil as per the variations in temperature.

The engine lubricant should be able to flow in all the ranges of the temperatures, even in the lowest of them, so that there is minimal contact between the metal components. The lowest temperature at which the lubricating oil stops pouring or freezes literally, is known as the pour point. As per the SAE specifications, the ‘Cold Cranking Simulator(CCS)’ and the ‘Mini Rotary Viscometer(MRV)’ are the properties related to pour point, which are required for specifying the motor oil in extreme cold conditions. Also, due to the high affinity of carbon, the oil has the tendency to burn if ignited. Thus, the lowest temperature at which the ignition of the oil takes place is called flash point. For a good engine lubricant, the flash point should be as high as possible.

Since the engine lubricant is an oil, it can be acidic or basic in nature. It is this condition, where Total Base Number (TBN) and Total Acidic Number are taken under consideration. TBN refers to the ability of the oil to neutralize acids, whereas TAN is the measure of how the oil can neutralize bases.
 

WHAT ARE THE DIFFERENT GRADES OF THE OIL?

For these numerous and varying conditions, it’s pretty obvious that the engine oils should behave different for different situations. Thanks to the observational studies of the Society of Automotive Engineers (SAE), what we have got is a numerical code system, which basically describes the behavior of oils on the basis of their characteristics of viscosity through different gradings. These viscosity gradings range from a viscosity as low as 0, to the viscosity index till 60: 0,5,10, 15, 20, 25, 30, 40, 50 or 60. A suffix of ‘W’ is designated to the viscosity of 0, 5, 10, 15 and 25, indicating that these viscosities are for lower temperatures, say “winter” conditions. The viscosity 20 comes with either W or without it, depending on the temperature. The viscometrics of these different grades of engine lubricants are defined in the document SAE J300.

The grading of the engine lubricants is defined under two types:-

Single Grade –The engine oils defined under this section has 11 viscosity grades, out of which 6 are considered as low-temperature lubricants and are given a designation of W. The 11 grades are namely 0W, 5W, 10W, 15W, 20W and 25W for cold conditions and 20,30,40,50 and 60 for warm conditions. The dynamic viscosity of the oils with the ‘W-suffix’, i.e., single winter grade oils, is measured using two methods – Cold Cranking Simulator (ASTMD5293) and Mini Rotary Viscometer (ASTMD4684). Similarly, for the single non-winter grade oils, the dynamic viscosity is calculated at a temperature of 100 °C. If the viscosity is higher, the SAE viscosity grade is also higher.

Multi Grade – In most of the vehicles used nowadays, the engines are exposed to the extremities of climates and temperatures. In such situations, the engine has to perform brilliantly in cold as well as warm conditions. To make the engine oil perform well under such differences, some additives (viscosity index improvers) are added to it. Due to this, the engine oil has both winter and no-winter grades, which enables only one kind of oil to be used in all seasons. The SAE designation of such oils generally involves two grades. For instance, if the oil is designated as 10W-30, the first number 10W is the oil’s viscosity at lower temperature and the second number represents the viscosity of the oil at 100 °C.

WHAT ARE THE OTHER ADDITIVES?:-

Apart from the viscosity index improvers for the multi-grade engine oils, the engine oils are often added with certain additives to keep the surface of the engine clean and protected from internal corrosion, acidic oxidation and formation of any kind of sludge. Following are the different kinds of chemical compounds used as additives for the engine lubricants of motorcycles:-

Zinc Dialkyldithiophosphate – It is an anti-wear chemical, which is used to protect the metallic surfaces of the engine components with zinc or any other compound.

Calcium Sulphonates – These are added to prevent the engine lubricant from breakdown due to oxidation and thus resulting in negligible formation of oil sludge deposits.

Molybdenum Disulphide – This chemical is used to reduce friction during metal to metal contact and results in anti-wear conditions.
 

WHAT ARE SYNTHETIC OILS?:-

In order to replace the mineral lubricants, synthetic engine lubricants were first introduced in the mid 1970s, which have the ability to remain in fluidic state even in extreme low, sub-zero temperatures. These oils have the same grading system under SAE specifications for their viscosity designations, as the normal engine oils do have. These oils are generally derived from bases belonging to Group III, Group IV and Group V, and include lubricants such as synthetic esters and poly-alpha olefins. Due to higher purity, the synthetic oils exhibit better properties at the extreme ends of the temperatures, over the traditional petroleum-based engine lubricant. They also degrade slower than the conventional engine oils, due to their lower requirements of viscosity index improvers. Since they too get clogged with particulate matter similar to normal engine oil, these oils also require periodic filter and oil change, but after a longer interval in comparison, as a result of decreased degradation.