LUBRICATING OIL.

Press, Volume LXI, Issue 18400, 5 June 1925, Page 5

LUBRICATING OIL.

USE ON CARS. QUESTION OF FUEL CONTAMINATION. Kvcrv owner of a motor-car ought to have some idea of lubricants r>nd whit happens to them iu service. The motor manufacturers generally see to it that owners are supplied vrith instructions as to what v.avts oi the car want oil or grease, or how 1 recently these lubricants should be supplied. Sometimes manufacturers vecommend a particular brand of oil, but as thev occasionally change their recommendations— suggesting one oil tnis year and a different one next vea | owners are inclined to discount t-nc value of these recommendations. Undoubtedly the most important change that an engine oil undergoes while it is in the crankcase is dilution with fuel (motor spirit) It is.B en «\T allv recognised that a lubricating on does not "wear out" to any appreciable extent if no contamination with niei took place and assuming the oil was a suitable one lor the work—there is no reason why an oil should not remain in service indefinitely. But contamination does take place, and accordingly motorists are recommended to ciiaiu off the oil from the crankcase periodically and All. with now oil. In the U.S. it is common to c > ia ,'!£ e oil evcrv 500 miles, but in Great *>"- tain a change every 1000 miles is considered sufficient for most cases, although it is undoubtedly better ■ vo change more frequently. The amount of fuel contamination, varies and depends on a great many tjwitms. According to an American estimate «>s quite usual to find 25 per cent, to &J per- cent, in the winter and 5 per cent, to 10 per cent, in the summer The same authority writes: "»>»«*"" can best bo minimised by. obseivyig some cars in driving, particularly • starting. More trouble can be caueca bv holding out the choker lor a ten minutes than can be remedied in a long time. In less than aminute half a pint of motor spirit can be thrown into the crankcase by this means, -liven the best piston rings cannot bo expected to stop it all. Idling the engine for long periods will also cause flooding and always a cold engine will be worse than a hot one." The effects of the crankcase dilution depend on the condition of the engine and the nature of the lubricant.. Ine lubricant will in any case htwe its vis•cosifcv (or thickness) considerably i&duced, but this is not necessarily so serious as it- sounds. Many oils dope: almost entirely on their viscosity i< givo good results and the efficiency o «uch is of course seriously impaired by dilution. But oils which have l friction-reducing properties are less affected by dilution -and indeed soma authorities go so far as to maintain that they are just n* good when diluted as new. They will, however, have lost in viscosity and ma 1» less effective at sealing the piston rings, resulting in loss of compressw. and lioisy engine Lubricating oils made on the yYeii, and iSouthcombe process have higher friction-reducing properties than oilier. oils and are. therefore loss affected fuel dilution. . , . The general condition of the engine has much to do with dilution. An engine which is worn relies on We lubricant to do what really ought to be. done by pistons, cylinders, or rings. When this is the case taie dilution or the oils is more serious owing to tfi€ reduced viscosity and consequent inability to .act as a kind of packing. ' It sometimes happens that gets into the crankcase, having come froiii the combustion chamber in the form of vapour. Under such circumstances this water may wash oil from the metal surfaces, and in this respect it is again worth remembering the unique properties of oils madia on the process mentioned. This process lowers the surface tension of the oils, resulting in a comparatively low interfacial tension between the oil and metal surface (of bearings, pistons and cylinder walls ; etc.). Wells's perm process oils ' cling; to the metp.l surfaces they have to lubricate and form strong Alms which, are not easily washed off. . . When water and motor spirit get into the crankcase they usually carry with, them dirt and grit which mostly come in the first place from ror-d ciust Needless to sa.v this foreign matter is a serious disadvantage), as it acts as an abrasive. It is estimated that somo engines will show as much as 2o per cent, of solid and asphaltie matter m the oil after it has been in use. _ In conclusion it is worth emphasising that the working conditions of alnptor oil are far from ideal and that the belt results will l-o obtained when oils of exceptional efficiency are used.,"

With a view to impressing on members the requirements of the regulations as to motor drivers' licenses under "the Motor Vehicles Act, 1924, Mr J. S. Hawkes. secretary of the Canterbury Automobile Association has sent out' the following circular: —Important to ear owners, —I would point out that it is necessary, under this Act, that everv driver of a motor vehicle must procure an annual license to drive. This is quite separate -and distinct from the annual license to use of £2. This license applies not only to the owner of the car. but also to every individual' who drives the car, whether husband, wife, son, daughter or emplovec. The license must be obtained Iroin the local authority in the district in which the driver exists. The charges navable by each owner*may be summarised as follows: —Registration (first year only), £1; registration plntes. 2s; license to use (payable annually), £2; license to drive (payable annually), 6s.