The viscosity of the oil for any application depends on the speed, load, and the clearance between moving parts, type of lubrication and finally the ambient temperatures. Oil must provide protection over a wide range of temperatures from cold starts to long hauls. When oil does well at both extremes it gets a “multi-grade” rating that includes a number/letter followed by W and a number, such as 20W40. In a hot climate or driving through a region where a combination of high heat and high-altitude are encountered, the operation & maintenance manual provided by the manufacturer, will probably give suggestions for a multi-grade or “all-season” oil such as 15W-40. Such oil has the cold flow characteristics of 15-weight at start-up, yet the coating and protecting property of 40-weight oil at the high temperatures. In a predominantly cold climate, the recommended oil might be a 5W-30. However it is advisable to be guided as given in the operation & maintenance manual of that equipment

In general, the functions of engine oil are as under: > Permit Easy Starting. > Lubricate and Prevent Wear. > Reduce Friction. > Cool Engine Parts. > Minimize Combustion Chamber Deposits. > Protect Against Rust and Corrosion. > Seal Combustion Pressures. > Keep Engine Parts Clean.

Lubricant is a substance interposed between two surfaces in relative motion for the purpose of reducing the friction and wear between them. Lubricant provides a protective film which allows for two touching surfaces to be separated and "smoothed," thus lessening the friction between them and correspondingly less heat generation

The benefits of multi-grade oil are as under: Multi-grade oil is thinner at low temperatures and as such the oil from the sump reaches all parts of the engine quicker than mono-grade oil as soon as the engine is started thus it reduces wear to that extent. Multi-grade oils enable better fuel economy than mono-grade oils. As multi-grade oils tend to be thinner at low temperatures and thicker at high temperatures than mono-grade oil it offers better protection to the engine. Thus it reduces oil consumption.

Higher quality engine oil is needed for turbo charged vehicles as they have better fuel combustion thereby increasing thermal load on engine oil and soot production is increased.

The performance levels of chemical properties relating to detergent action and dispersion in the two engine oils are different. Accordingly API service classes have two general classifications: S for gasoline engines and C for diesel engine. It is possible for an oil to conform to both the gasoline and diesel standards. (Note: Combined API Service Classification motor oils are highly effective at reducing and controlling sludge and varnish deposits, acid and foam formation and have improved oxidation stability. Most of the oils in the RZR range meet such minimum levels and therefore possess the required standard and accordingly they are suitable for both petrol and diesel engines.)

The oil pressure may drop because the oil has thinned down considerably, due to fuel dilution. It could also be because of insufficient oil in the system, either because of an oil leakage or excessive oil consumption or even possible oil pump failure, causing the oil to not circulate. Check the oil level in the sump and also for fuel dilution. If both seem to be in order, check the vehicle for pump failure or any other mechanical problem.

External oil leakages from areas like tappet cover, oil filter bowl, timing cover oil seal, rear main oil seal (flywheel side) or at some other point in the oil circulation system. Thinning of the oil due to fuel dilution. Excessive clearances between the piston and the cylinder can cause high oil consumption, as a little oil gets thrown into the combustion chamber during the process of combustion when the piston moves up and down, resulting in it also being burnt.

One of the reasons can be overheating of the engine parts, due to little or no lubricant present in the system, resulting in friction which, causes micro welds in the engine, and ultimately leading to seizure of the engine. The seizure could also be caused by over thinning of the oil, due to fuel dilution. The major reason could also be operational problems and not the oil. Further if the engine becomes overheated due to any other reason viz. the cooling system not working properly or driving overloaded truck for a long period etc. the engine could still seize.

The performance enhancing additives of the oil viz. TBN, anti-wear, ant-oxidant etc. gets used up in service and below certain levels the oil will not be in a position to protect the engine. Oxidation of the oil beyond certain limits will start corroding the equipment or leave unwanted deposits on the moving parts. Further contamination of the oil with water, dust, dirt and soot from combustion products shall cause corrosion and abrasive wear. In view of these reasons that we need to change the oil once it looses its useful life to protect the engine.

The best way to judge whether the oil’s life is exhausted is to test a sample in the lab. If the TBN has decreased a lot from its starting value and/or the viscosity has increased or decreased substantially, the oil needs to be changed. Since it is not possible to test the oil in the field, it is suggested to look into the following warning signal: Colour - oil has turned black. This could be due to excessive oil oxidation or heavy contamination of the oil with soot. Smell - oil emits a burnt odour. This is caused due to dilution of the oil by fuel seeping into the oil circulation system. The oil tends to become less viscous and smells burnt. Oil’s viscosity - increased or decreased substantially (judged by rubbing the oil between the fingers). Oil’s viscosity increases substantially due to excessive oil oxidation or heavy contamination of the oil with soot and decreases substantially due to dilution of the oil by fuel seeping into the oil circulation system.

The engine oil used in four stroke 2 wheelers/3 wheelers lubricates the engine, the wet clutch and the gears. It needs to take care of higher temperature operating condition since the engines are air-cooled unlike the passenger car engines which are cooled by water or by a Coolant. Further, it should have controlled friction characteristics to take care of the wet clutch requirement. Thus 4T oil fortified with special additives is required for 4 Stroke Motor Cycle Engines.

Two stroke motorcycle/scooter’s engine may either have a premix system or a separate oil injection system. In the former, lubricating oil is mixed while filling petrol in a particular proportion. In case of a separate oil injection system, the lube tank is simply filled as there is an in - built unit in the vehicle, which controls the flow of oil in petrol.

Two-Wheelers generally have a 2-stroke engine inside it, which works differently from a 4-stroke engine present in a car or truck. Truck and car engine oils contain additives, which results in higher deposits and smoke and that will lead to spark plug fouling if used in 2 wheelers. Further truck and car engine oils do not contain a solvent, which is required for a 2-stroke engine because it has to mix with petrol.

Improper combustion of bad quality/adulterated fuel causes abnormal increases in load on the engine which in turn affects the performance of engine oil. Further the by products of improper combustion, shall damage the composition of lubricant if by chance it goes into sump, thereby effecting the overall performance of engine oil.

Two-Wheelers generally have a 2-stroke engine inside it, which works differently from a 4-stroke engine present in a car or truck. Truck and car engine oils contain additives, which results in higher deposits and smoke and that will lead to spark plug fouling if used in 2 wheelers. Further truck and car engine oils do not contain a solvent, which is required for a 2-stroke engine because it has to mix with petrol.