Engine oil quality
Engine oil quality
Keywords: Crude oils, Engine oils, EOLCS, IEA
The range of motor oils currently available is huge, there being some hundreds of brands in the UK alone; such variety can be a potential source of confusion to a prospective purchaser not having specialised knowledge. Package marking is often not overly helpful in that whilst emphasis is placed on brand image and possibly viscosity rating, the all-important performance specifications are often hidden away in comparatively small print. Even then, the performance claims themselves can be confusing, since a number of performance specifications are often displayed. Price differences between products are considerable, varying by as much as a factor of ten. What is not so obvious are the differences in "quality" levels between the various products, although there are many differences in the definition of quality. In this instance, the definition of "quality" is taken to imply a "degree of excellence", or even "fitness for purpose", although the definition "conformance to a specification" can also be relevant. The quality(degree of excellence) of a motor oil is dependent on the composition and nature of the base fluid and of the nature and content of any additives. Mineral oil base fluids can range from mildly-refined basestocks, or even re-refined oils,to severely-refined products which can approach the general properties and performance of synthetic basestocks. At this point, it should be emphasised that the term re-refined should not necessarily imply inferior quality, since the nature of the refined product will reflect the nature of the re-refining process. Synthetic basestocks are, as the term implies, manufactured and are normally in the form of a polymer, such as polyalphaolefins, polybutenes,polyolesters, polyalkylene glycols, etc., or as esters such as aliphatic di-esters. Additives vary widely in composition, and are present to improve the existing qualities of the base fluid, or to impart new properties. Higher prices are associated with the use of higher additive incorporation levels, also the use of synthetic basestocks.
The API and ACEA claims are intended to provide some sort of guarantee to the prospective purchaser that the oil in the container meets all of the criteria defined in the relevant specification. However, as can be seen from after-market auditing experiences,such guarantees are not necessarily valid, which is a cause for concern, and will no doubt be a subject for increasing debate between the interested parties.
Although in 1997 API progressed three significant enforcement actions as a result of findings from its aftermarket auditing programme, there is concern that the typical historical failure rate of 1 per cent represents 10 million gallons of sub-quality motor oil capable of causing possible engine damage being sold annually in the USA. Because of the elapsed time, any subsequent enforcement actions are usually far too late to prevent unsuspecting users, although beginning with the 1998 audits,API now notifies the licensee of testing results within 30 days to reduce the possibility of adverse effects on potential users. A 1 per cent failure rate would not be acceptable in many other industries. Also, this failure rate is ascribed only to those samples which are so poor as possibly causing engine damage. It was confirmed that sub-specification products failed almost entirely as a result of low additive treat levels; viscosities were virtually 100 per cent satisfactory. What is not clear is the proportion of oils which contain additive levels sufficient to provide reasonable levels of performance, but are likely to be below those levels specified in the approved formulation, thus enhancing profitability levels for the manufacturer.
In addition, the Standards Division of North Carolina reported that of the 1,420 samples of bulk oil collected in 1996, 3.5 per cent failed to meet the SAE viscosity requirements. While of concern, the proportion of failures had in fact showed a steady improvement from the 10 per cent experienced when the monitoring programme started in 1992. Failures were attributed to poor management, inadequate inventory controls and a failure to clean out manifolds between successive deliveries of products. Also, some 2,400 samples of packaged oil were collected in 1996, and of these, 4.9 per cent failed the SAE viscosity requirement. Although failures in viscosity of bulk samples can be attributed to inadequate line flushing, etc., why the failure rate in viscosity associated with packaged samples should be so much higher than that experienced by the API EOLCS is not clear.
The API system, relying on aftermarket auditing, represents the classic "quality control" approach, with all of its attendant limitations. By identifying problems after the event, it is too late to take any sort of effective corrective action to remedy that particular situation. Also, because of the costs involved, the scope of auditing and analysis is limited to the carrying out of only a very limited range of tests on only a small fraction of products on sale at any one time. Even with these limitations, it has been already established that the incidence of 1 per cent for relatively major non-conformances is far too high, exceeding established limits in many other areas of manufacturing industry.
The ACEA system, which stipulates that the requirements of the ATIEL Code of Practice are incorporated into the existing quality systems of organisations so as to enable auditing to be carried out on a regular basis by external and experienced auditors,represents a sounder "quality assurance" approach. If these requirements are properly embodied into quality systems, any potential problem areas should be rectified at source, and there should be no scope for sub-specification manufacture. However, yet again there are fundamental problem areas which have not as yet been satisfactorily addressed. The requirements of the ATIEL Code are complex and represent a considerable extension to the quality system. The accreditation bodies, responsible for conducting external audits, base the auditing scope and frequency and depth on the basis of an organisation's activities. The incorporation of the ATIEL requirements will considerably increase the complexity of audits, and the accreditation bodies have not as yet been involved in the process in sufficient depth so as to properly reassess the need for increases in audit scope, depth and frequency. It is clear that if the auditing requirements were to be uprated to such an extent so as to properly meet the needs of EELQMS, auditing costs would be substantially increased. There would appear to be an urgent need for ACEA to consult with the accreditation bodies so that the full significance and consequent implications of"contracting-out" these compliance aspects are fully understood and appreciated.
More manufacturers are moving towards more extended drain intervals. In August, all new gasoline Peugeot models moved from 9,000 miles (or one year) to 20,000 miles (or two years). The new Cadillac Seville STS is designed for 100,000 major service intervals. As a result, lubricants will experience increased stress, and the consequences of any shortcomings in their manufacture will be even more pronounced. All of the considerable technology and expenditure involved in designing engine oils to meet more stringent criteria is to no avail if the contents of the oil package are not to the intended standard due to manufacturing deficiencies. In approximate terms, the annual UK motor oil volume is 400 million litres. This is equivalent to some 40 million sump changes per year if we assume an average sump capacity of ten litres. If our failure rates are similar to those exposed by the American aftermarket audit figures, this would indicate that some 400,000 engines annually are therefore destined for an early visit to the scrapyard, or at least a major overhaul, due to inadequate quality procedures practised by the lubricant manufacturer.
