ENTERPRISES PVT. LTD.

Call us at 91-22-29209201
E-10 NANDDHAM IND. ESTATE.,
MAROL MAROSHI ROAD, ANDHERI (E)
MUMBAI (INDIA)
Tel: 91-22-29209201 Fax: 91-22-66938662
E-Mail : mytol@vsnl.net
 

  INTRODUCTION
 


The automobile industry is the major user of lubricants. Engine designs have been continually improved to reduce weight, increase fuel economy, increase power output, and at the same time meet environmental emission guidelines. Research is ongoing to formulate lubricants to meet the demands of the redesigned engines. In general, a lubricant must perform nine functions for the efficient operation of the engine.
 

  PERMIT EASY STARTING
 
An engine oil must be thin enough when first starting the engine to allow for sufficient cranking speed. The oil must then be able to flow immediately to lubricate vital engine components. Most of the engine wear occurs at start-up before the oil can reach all the engine parts. As the engine is heated, the oil must not become too thin and be unable to provide adequate engine lubrication. The viscosity of the oil is the measure of this resistance to flow.

The effect of temperature on viscosity varies widely with different types of oil. The standard used to measure the amount of viscosity change with temperature is the Viscosity Index (V.I). An oil with a high viscosity index shows less change in viscosity over a wider temperature range. Refer to the Glossary of Terms, and the Additive section of this site for more information. A "multi-grade" oil has a high viscosity index.

Synthetic oils have the best low temperature flow characteristics, and are worth the extra cost in northern climates during the winter months.
 
  LUBRICATE AND PREVENTIVE WEAR
 
The engine is now started, and the oil is being circulated by the oil pump to the engine parts. The oil must now prevent the metal-to-metal contact that will result in wear to the moving parts.

Full-film lubrication occurs when the moving surfaces are continuously separated by a film of oil. The viscosity of the oil must remain high enough to prevent metal-to-metal contact. Wear will only occur if the surface is scratched by particles thicker then the oil film. Crankshaft bearings, connecting rods, camshaft, and piston pins normally operate with full-film lubrication.

In some conditions, it is impossible to maintain a continuous oil film between the moving parts. Intermittent metal-to-metal contact occurs because of high spots on sliding surfaces, during engine starting, and in new or rebuilt engines. Lubrication under these conditions is referred to as boundary lubrication. This lubrication is accomplished by the additive package in the oil. Refer to the Glossary of Terms for further information on boundary lubrication.
 
  REDUCE FRICTION
 
Under full-film lubrication conditions, the film of oil prevents metal-to-metal contact. The viscosity of the oil should be high enough to maintain the film. A delicate balance must be maintained. If the viscosity is higher then required, the engine must overcome the excess fluid friction.

It is important to note that the viscosity of the oil changes as it becomes contaminated. Dirt, oxidation and sludge will increase the viscosity of the oil while fuel dilution will reduce the viscosity. This is the reason why the oil must be changed as per the schedule in the owners manual.
 
  PROTECT AGAINST RUST AND CORROSION
 
Under perfect conditions, fuel burns to form carbon dioxide and water. For each gallon of fuel burned, a gallon or more of water is produced. Most of this water should escape as a vapour out of the exhaust, but some does condense on the cylinder walls. Also, water passes by the piston rings and becomes trapped in the crankcase. This is more of a problem in cold weather before the engine is warm.

In addition to water, other corrosive combustion gases also get past the rings, and are dissolved in the crankcase oil. Add to this the acids formed by the normal oxidation of oil, and the potential for rust and corrosive engine deposits become significant.

Corrosion inhibitors are part of the additive package to protect non-ferrous metals by coating them, and forming a barrier between the parts and the acids. Also, rust inhibitors are added to the oil to protect iron/steel surfaces from oxygen attack by forming a protective screen.

Under full-film lubrication conditions, the film of oil prevents metal-to-metal contact. The viscosity of the oil should be high enough to maintain the film. A delicate balance must be maintained. If the viscosity is higher then required, the engine must overcome the excess fluid friction.

It is important to note that the viscosity of the oil changes as it becomes contaminated. Dirt, oxidation and sludge will increase the viscosity of the oil while fuel dilution will reduce the viscosity. This is the reason why the oil must be changed as per the schedule in the owners manual.
 
  KEEP ENGINE PARTS CLEAN
 
For a variety of reasons, a gasoline or diesel engine does not burn all the fuel completely. Some of the partially burned gasoline or diesel fuel undergoes complex chemical changes during combustion, and under some conditions forms soot or carbon. Most of the partially burned fuel escapes in the form of soot through the exhaust, but part escapes past the rings into the crankcase. This combines with water to form sludge, and varnish deposits on engine parts. Sludge buildup may clog oil passages which reduces oil flow. Varnish buildup interferes with the proper clearances, restricts oil circulation, and causes vital engine parts to stick and malfunction.

Straight mineral oils have a very limited ability to keep these contaminants from forming sludge within the engine. Detergents are part of the additive package to clean-up existing deposits in the engine, as well as disperse insoluble matter into the oil. Dispersants are also part of the additive package. Both detergents and dispersants attach themselves to contaminated particles and hold them in suspension. The suspended particles are so finely divided that they can pass harmlessly between the mating surfaces, and through the oil filter. This contamination is removed when the oil is changed. Another good reason for your scheduled oil change!
 
  MINIMIZE COMBUSTION CHAMBER DEPOSITS
 
Under perfect conditions, fuel burns to form carbon dioxide and water. For each gallon of fuel burned, a gallon or more of water is produced. Most of this water should escape as a vapour out of the exhaust, but some does condense on the cylinder walls. Also, water passes by the piston rings and becomes trapped in the crankcase. This is more of a problem in cold weather before the engine is warm.

In addition to water, other corrosive combustion gases also get past the rings, and are dissolved in the crankcase oil. Add to this the acids formed by the normal oxidation of oil, and the potential for rust and corrosive engine deposits become significant.

Corrosion inhibitors are part of the additive package to protect non-ferrous metals by coating them, and forming a barrier between the parts and the acids. Also, rust inhibitors are added to the oil to protect iron/steel surfaces from oxygen attack by forming a protective screen.