Words: Piyush Sonsale
Photography: Sanjay Raikar
An internal combustion engine without engine oil is like a body without blood. When the oil level is low, the condition is comparable with that of a dehydrated athlete.
The reasons are not far to seek. Being a contraption of mechanical linkages, the metal parts of an engine exert mechanical force on each other. This entails an evil – a destructive phenomenon called friction. Friction grinds the metallic parts and causes wear. Also, as the process is exothermic, it increases the engine’s temperature above optimum levels, which, in turn, causes the metal parts to expand and fuse into each other to seize the engine. In short, in the absence of oil your vehicle can be dead by the time you ride back home from the showroom or maybe earlier.
The primary function of engine oil is lubrication to avoid friction. Barring the area in an engine’s cylinder between the piston head and the combustion chamber, every other part is soaked in oil. Channels and perforations are made in the components for the passage of oil. Oil forms a separating film between the connected parts to avoid friction. However, it still doesn’t make the engine completely friction-free. Frictional grinding creates microscopic rubble, which again mixes with the oil. This saves it from scraping against the metal parts, but, in the process, the oil becomes contaminated. Oil drains down by gravity and is collected in a collector called a sump. An oil filter cleans the oil by removing these microscopic particles and other waste. An oil pump then recirculates the oil throughout the engine and so on.
Since oil keeps flowing continuously, it also absorbs and takes away excess engine heat by convection. Anti-oxidation additives in the oil prevent oxidation of the metallic components while acid neutralisers guard it against acids formed during combustion. Oil also seals the gap between the piston and the cylinder liner. Reduced friction ensures optimum efficiency in the engine’s working, which helps in saving fuel. Now that we know we can’t ignore it, let’s see how engine oil is made.
What’s in the oil?
Engine oils are basically hydrocarbons reinforced with additives to give them specific properties. These oils have higher flash points (temperatures at which they give out inflammable fumes) to be able to handle engine heat.
Oil types: The basic difference in engine oils lies in their origin, which can be from nature or artificial. The second distinction is their ‘kinematic viscosity’ (time taken to flow down a surface when subjected to gravitational force) and ‘absolute viscosity’ (resistance to flow when under pressure). The higher the kinematic viscosity, the better the oil settles on engine parts when the engine is not alive. Oils with high absolute viscosity resist flowing when forced by the oil pump, which is not favourable. The rate at which viscosity changes (viscosity index) also defines the type of oil.
Mineral oil: Mineral oils are derived from naturally occurring crude oil. Its quality is then improved with certain additives. Price-wise these are the cheapest and also have the shortest life.
Synthetic oil: Synthetic oils are man-made. Their chemical composition is formulated in a laboratory and is then produced artificially in a controlled environment. These oils are generally polyalphaolefins (PAO) while some are ester-based. Esters are polar by nature (magnetic properties), so they stick on metal surfaces, maintaining an oil film. However, the production cost of ester-based oils is high, making them rather expensive to buy. Synthetic oils have very low or no wax content, which is the culprit for oil condensation.
Semi-synthetic oil: As the name suggests, semi-synthetic oils stand between mineral and purely synthetic oils. These are generally mineral oils blended with synthetic ones and serve as a compromise between the two.
Considering the price, synthetics cost much more than mineral oils while semis are costlier, but close to minerals. However, synthetic oils can sustain extreme temperatures and pressure and also double the vehicle’s oil change interval. Thus the increase in the price justifies the brew. More so if the vehicle is used in extreme conditions, on harsh terrain or is not maintained properly.
In each of these three types, the following additives are added in varying proportions to further enhance the quality of the oil.
Viscosity index improvers (VII): These chemicals make the oil less susceptible to viscosity change as a result of variations in temperature.
Corrosion inhibitors: Anti-oxidants are added to prevent oxidation.
Acid neutralisers: These are added to absorb and chemically neutralise acids, such as sulphuric acid formed in the engine.
Pour point depressants: Pour point depressants increase the ability of oil to flow at low temperatures. This helps during cold starts.
Anti-foaming agents: These are helpful in avoiding the formation of foam in the engine.
Detergents: These help in cleansing the engine from within.
The Society of Automobile Engineers (SAE) is a worldwide association of engineers with regional subsidiaries. The Society sets standards in the automobile, aerospace and industrial fields. The SAE has conducted globally accepted viscosity tests on engine oils at high (100º C/212º F) and low (0º C/32ºF) temperatures to classify them according to their grading system. Every oil company mentions these grades on their engine oil cans.
The low temperature grades are suffixed with a ‘W’ to denote winter viscosity.
The higher the number, the thicker the oil at cold temperatures. For instance, 0W, 5W, 10W, 15W, 20W, 25W. The hot temperature grades only have the number. For example, 20, 30, 40, 50, 60.
Engine oils are also classified as single or multi-grade oils.
Single-grade oils: These are tested at either high or low temperature. They have only one grade. For example, 10W, 20, 50. These oils have little use in automobiles when engine and atmospheric temperatures vary. These are mostly used in industrial generators, lawn-mower engines or chain saws.
Multi-grade oils: These are tested at both low and high temperatures. Both the grades are mentioned on the oil. Automobiles generally use multi-grades as the same oil can be used at different temperatures. For example, 10W30, 20W50 etc.
For Indian conditions, the commonly used grades for motorcycles are 20W40 and 20W50. Oils with winter grades lower than 15 are recommended only in extremely low temperature areas.
Engine oil properties depend largely on the type of engine. Hence, engine oils are different for each type of engine. Since two-stroke engines are now obsolete, let us consider different types of four-stroke engines and their requirements. Nevertheless, two-stroke oils are still on sale. Oil cans with 2T written on them are meant for two-stroke engines. Four-stroke cans have 4T written on them.
Apart from grading, oils are also tested for quality by various national and international standards authorities such as the API, JASO, ACEA and ILSAC et al. For two-wheelers, JASO ratings are more relevant as they test the oil for conditions specific to those engines. However, some oil companies also mention API ratings. JASO stands for the Japanese Automotive Standards Organisation. Currently MA, MA1 and MA2 are the ratings for motorcycles with high friction levels (no anti-friction additives) while the MB rating is given to the ones with low friction (containing anti-friction additives). Manufacturers who get their oils tested by JASO mention the rating on their packaging with the JASO symbol while others just claim the JASO rating based on their own tests.
Do’s and Don’ts
In order to change the engine oil in a motorcycle, drain out the old oil completely and tilt the bike for a while until the last drop jumps into the collector. Plug the drain outlet and pour the exact amount of new oil as prescribed by the manufacturer. If you are running on semi-synthetic or synthetic oil, a delay of up to 1,000 kilometres more than the prescribed oil change interval is pardonable. However, as the oil filter cleans the engine oil during every cycle, it is bound to get saturated with waste over a period of time. Therefore, it is necessary to change the filter at alternate servicing or at least have it cleaned if it is just a strainer when shifting from mineral to synthetic oil.
Apart from quality, the volume of oil in the engine is also important. To check the oil level, unscrew the plastic plug found on the engine. The plug is connected to a shaft called the ‘dipstick’, which has a measuring scale on its surface. Wipe it clean, insert it back into the engine but don’t screw it. Pull it out again and read the oil level on the scale. If found low, top up the engine until the level rises to the prescribed volume, but never overfill the engine with oil.
Sludge or ‘black death’, as infamously known, is the ‘dark side’ of an engine oil. Sludge is a black, tar-like substance that engine oil gets converted into. Exposure to extreme engine temperatures, transmission pressure, wrong engine oil or, in some cases, a faulty engine design changes the chemical composition of the oil in time. The black waxy substance thus created is called sludge. Sludge causes engine seizure and deterioration of the engine’s organs as it
does not flow through the engine, causing wear. If you find a whitish paste inside your engine, it is oil change time for sure, but the substance is not sludge. It either means that the engine gasket has a leak and the coolant has mixed with the oil or else the engine was cranked when under water and water has mixed with the oil. The only remedy in such cases is oil change with flushing. Flushing is a process of cleaning the engine internally. Fill up the engine with a cheap mineral oil, crank it up and drain out the oil after a few minutes. Then pour in fresh oil.
Waste oil disposal
Now that you have learnt to change the engine oil of your bike on your own, what to do with the waste oil? Flush it down the toilet? Consign it to the dustbin? Bury it in the garden or just throw it over the fence? Never! Waste engine oil is a highly hazardous toxic pollutant. It should either be submitted to a recycling or disposal plant or used as a lubricant in household appliances such as sewing machines, bicycles or gymnasium equipment.
Yes, you can store a can of engine oil for as long as you want, even when the can has already been opened. However, if your vehicle is about to remain unused for a long time, do not drain the oil to store it. Always leave the oil in the vehicle, as it helps in avoiding engine corrosion.