REQUIREMENTS OF A LUBRICANT.

King Country Chronicle, Volume XXV, Issue 3404, 15 December 1931, Page 7

REQUIREMENTS OF A LUBRICANT.

A previous article dealt with the importance of accurate control of basic materials, refining processes and blending in the production of high-grade motor oils. . The following notes dealing with specific requirements of a motor oil would indicate how each characteristic or function must be carefully studied and not left to guess work. The primary work that a motor cylinder oil is called upon to carry out is to reduce friction and dissipate heat. The oil also acts as a sealing medium between piston and cylinder walls to enable the necessary compression to be given to the combustible gases. The friction-reducing properties of an internal combustion engine oil are influenced by: (a) The inherent quality of the oil itself; (b) viscosity; (c) contamination through carbon formation; (d) sludge formation; (e) contamination by dust and water.

The essential properties of highgrade motor oils are: (a) Maximum friction-reducing properties; (b) minimum carbonisation; (c) low sludge tendencies; (d) absolute purity of the oil itself. This article will 6e confined to sections (a) and (b.) Solid friction, resulting from metal to metal contact when one surface moves over another, can be substituted by fluid friction due to a film of oil being placed between the rubbing surfaces.

It is impossible to completely overcome friction in a motor engine. However, the friction can be considerably reduced due to the lower friction between oil films as against metal Burfaces in contact. When we exclude the influences of contaminating agents such as dust, metal and water it can be given by: (a) the oil which in itself possesses maximum frictionreducing properties, and (b) the lightest bodied oil that can be used in a particular system. The term "oiliness" applied to lubricating oils is quite a common one, and, while it is not possible to definitely express "oiliness" as we can viscosity, flashpoint and cold test, it is well established that certain lubricating oils have greater "oiliness" or greater friction-reducing properties than others.

It is here that the initial quality of the basic material and refining treatments arei made evident. Low quality, poorly refined oils are deficient in lubricating properties and have a low "oiliness," and will be responsibile for excessive wear taking place.

Viscosity, or body, is the other important factor influencing friction reduction. Viscosity is a method of expressing comparative thickness or thinnes of various oils. All minerals oils have a tendency to increase in viccosity with drop in temperature and to thin down or have lower viscosities at increased temperatures.

In view of the friction which actually exists when one film of oil is moved over another, it is essential that to obtain the maximum power output from the engine the lightest viscosity oil that will suit the particular system to be used. The chief object of blending motor oils is to ensure that suitable viscosities are provided to meet the operating conditions met with. Seeing that engines must be started up when external temperatures are very low, and as the same oil must operate when considerable heat has been developed, a wide range of conditions must be catered for. It is worth the object of meeting these variations in operating conditions influenced by temperature and engine design, tha t every oil company markets a range of motor oils, as it is not possible to use one oil to suit all lubricating systems. The actual number of grades and qualities marketed , follows on a considerable amount of research. It is essential that the grades be kept uniformed, and it is here that control laboratories are necessary to supervise blending operations. Obviously, the small oil blender who generally slavishly follows what someone else has done is not in a position to supply oils which will give efficient results under the wide range of conditions met with. Generally, we find that such concerns utilise large percentages of heavy green cylinder oil with the object of giving the oil plenty of body. In so doing, however, the oil is made so heavy that at low temperatures starling troubles are experienced and a certain amount of heat must be generated through friction before the oil is reduced to such a state that it can operate in a particular system. Excessive wear and resultant maintenance charges are brought about by using oils deficient in lubricating [qualities. Therefore—do not take a risk.