ARE ADDITIVES WORTH WHILE?

Press, Volume CV, Issue 31000, 4 March 1966, Page 11

ARE ADDITIVES WORTH WHILE?

are s 0 battered by com-] peting claims for this! and that to make our cars last longer, run better, use less fuel, and perform miracles, that we are inclined, I think, to develop a general resistance to all of it, writes J- R. L. Anderson in the “Guardian.” On the whole cars perform well enough, the essential petrol costs so much—why spend more? This is certainly my feeling. But I am also nagged by a doubt: am I quite fair to my long-suffering car? Are additives to improve lubrication, to resist corrosion, to protect the radiator, and the like, a waste of money: or will they really help my car to help me? At my request I discussed these questions at length with Mr H. A. Gilby, group technical manager of Slip Products, and some of his colleagues in the Slip Group,

which markets a large range of additives to improve motoring performance. Mr Gilby and his colleagues were patient with me: they accepted that I was fairly sceptical, and we considered facts. A SHOCK The first fact is that if you look at a beautifully machined metal surface under a powerful microscope, you get a shock: it is no longer a i smooth surface, but more like those recent photographs <rf the moon, a mass of craters and little volcanoes. When one such surface slides against another in a car engine, it is obvious that something must wear. And something does. In an extreme case, if you use no lubricant at all, the metal surfaces will lock together and your engine will seize. The whole purpose of lubrication is to prevent this. Normal lubrication with any

good engine oil achieves its purpose quite well, but the film of oil is inevitably thin, and the stresses involved are great The theory behind the use of molybdenum disulphide additives is this:— The molecule of molybdenum disulphide is (roughly) a sort ot sandwich of an atom of molybdenum between two layers of sulphur atoms. The bond between molybdenum and sulphur is strong, but that between adjoining layers of sulphur is weak, so that the structure shears easily with little friction. The bond between sulphur and metal, however, is strong, so that a layer of molybdenum disulphide between metal bearing surfaces has the effect of “plating” the metal surface with a substance of an extremely low frictional resistance, and thus adds to the efficiency of the lubricating oil used. With newly-machined metal surfaces the friction of microscopic hills and valleys may produce a chemical change in the surface of the metal, which, if it is brought about gently, can be beneficial to later smooth running. Molybdenum disulphide added to engine oil is said to help in promoting this resurfacing. TESTS MADE Tests were carried out in the Department of Mechanical

Engineering at the University of Liverpool to measure (by using radioisotopes) the effect on piston ring wear of adding a “moly” preparation to engine oil. Over three tests, the additition of 5 per cent “moly” to the oil was found to reduce the rate of wear by an average of 25.4 per cent. The addition of 10 per cent of the additive gave less satisfactory results for reasons which are highly complex, and which, the test reports considers, may have been partly because of the nature of the test. The results of a 10 per cent admixture of the additive are held, therefore, to be inconclusive, as far as this particular test is concerned. The conclusions about the 5 per cent addition indicate a material reduction in the rate of wear. If such additives are of value, why don’t the major oil companies add them as a matter of course? This is one of the questions that has puzzled me, and made me sceptical about additives. There seems to be several answers. REASONS Firstly, cost; oil business is highly competitive, and since modern lubricants do their job well enough for most purposes, it is not commercially attractive to add to basic costs by including additives

in the selling price. Secondly, lubricating oils are used over a vast range of industries, and some uses might not benefit from additives. Thirdly, as with the car itself, manufacturers leave the provision of many gadgets to outside makers. It is a question of marginal performance. A car will go well enough without additives —my cars have for years. But it will go better with sensibly chosen additives, and you will almost certainly gain in engine life—l say “almost certainly” because engine life is determined by a wide range of treatment, not all concerned with lubrication. Part of the value of giving serious thought to additives is in the thought it provokes about the rest of one’s treatment of one’s car. During my motoring life I have not been an additive user. I shall shortly be changing to a new car, and I am going to experiment. Much of what I find is bound to be subjective—some of the results may show only to second and third owners of my car, long after it has been traded in.

But I think that the experiments are worth making: 1 shall at least convince myself whether it is worth adding marginally to my motoring costs to drive a more-cosseted car.