LUBRICATION.

Auckland Star, Volume LXIII, Issue 187, 9 August 1932, Page 14

LUBRICATION.

PREVENTION OF WEAR.

DISTRIBUTION PROBUBMi

SELECTING THE EIGHT OIL,

If two products will do a job of work equally well, then the cheaper of the two is the better proposition, but, before a decision can he reached, consideration of the work on hand must be given. What are the main tasks of a lubricating oil in the power unit of a motor car?

First, it must provide an oily film Which will attach itself to the metal parts to prevent wear. This film should resist being removed under conditions of high temperature, speed • and load. The oil should flow freely at all operating temperatures, even on a frosty winter morning, yet should not thin out excessively with increase in temperature—'but, it must be the correct grade for the job. Oils for automotive use should be well refined: and free from acids, moisture, resins, wax and asphalts or other impurities which may separate out or cause corrosion.

Any two metal surfaces, working together, must wear if they come into contact, but they can be separated by a film of lubricating oil preventing contact, provided the oil has the property of oiliness. Some oils have more of this property than others, and the more "oily" the oil, the better will it be able to penetrate between the surfaces, cling to tliem, and protect them from wear. Oiliness is the all-important factor in automotive lubricants.

What is the property of "oiliness," and what gives if? It is known that oiliness, or lubricity, is a property possessed by some oils which enables it to reduce friction, and therefore re-

duces wear. It is known that this property is inherent in certain types of crude oil to a greater extent than in others, and that careless refining methods can easily destroy, this property. Distribution of oil within the engine is an important factor. The lubricating 6ystem is designed to give effective, distribution, provided the oil is not too thick. An oil which will not flow, freely at the temperature prevailing when starting will not give effective circulation, and the surfaces are starved of oil until such times as the oil is sufficiently warm to circulate. A lot of wear can take place before this happens, and, in point of fact, nearly half the total wear in an engine takes place when starting up from cold.

Oils all'thin, out with heat, but some thin out to a much greater extent than others, and a poor quality oil which is sufficiently fluid to flow at starting temperature may'be much too thin at working temperatures, and wear takes place. A good quality oil should not thin out excessively with heat, and will therefore be sufficiently fluid at low temperatures to give distribution and yet have sufficient body at working temperatures to give circulation. In other words, high quality lubricating oil resists change in body with change in temperature.

Crude oils vary widely in composition and character. Some crudes naturally endow a lubricating oil with the quality of resistance, to heat, whereas others can only yield oils which thin out excessively.' Efficient refining methods are essential for treatment'of oils to remove harmful or undesirable substances, yet they preserve or foster the desirable features. The result of efficient refining of a well-chosen crude oil is a high-quality lubricating oil. It cannot be produced cheaply.