The oil becomes thicker as the temperature reduces and becomes thinner as the temperature increases. The operating temperatures encountered by the engines are above 100°C, so the mono grade oil (i.e.) SAE 40, 50 etc performs its expected duty during the normal operating conditions. However during winter months especially in the early morning the mono grade oil becomes very thick and starts giving lot of resistance during starting of the engine. Multi-grade oils take care of the viscosity requirement of the normal operating engines, as it does not become too thick during cold temperatures and too thin with increase in temperature.. 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.The viscosity changes with temperature will be very minimal in multi-grade oils, as multi-grade oils tend to be thinner at low temperatures and thicker at high temperatures than mono-grade oil.

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.

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 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 PALCO range meet such minimum levels and therefore possess the required standard and accordingly they are suitable for both petrol and diesel engines.)

Oil should be changed as per the equipment manufacturer’s recommendation after fixed hours of operation or after fixed kms. of running, provided the right quality of the oil is used as suggested by the equipment manufacturer. These change periods are established after extensive bench tests & field trials