Discussions focussed on the effects of marine fuel quality on engine lubricants, on fuel efficient automotive engine oils and on various base-stock related aspects of lubricants.
The first question from A. J. HARLOW (UK) related to the rising cost of marine fuels, referred to in the paper, which influenced current marine engine lubricant developments. C. G. A. EBERAN- EBERHORST, the main author, provided additional information by quoting data published in 1981 by M.
J. Briner et This showed that as a proportion of operating and capital costs of propelling machinery with 25 O00 shp slow-speed diesel engine, the combined cost of fuel and lube oil has almost doubled in the last 10 years to about 75% of total costs. This increase came in two steps associated with world oil price rises in 1973174 and 1978179. This was the major incentive to use lower quality (cheaper) fuels and to reduce fuel and oil consumption.
A further question relating to the fact that low quality marine fuel is one of the major problems for marine diesel engine lubrication was asked by K.
DATE (Japan) who sought the author's opinion on abrasive wear caused by the catalyst fines in FCC decant oil and whether this problem could be solved by the lubricating oil. The author replied that he saw no way in which lubricant quality could compensate for abrasive wear caused by particulate matter except possibly by using a higher viscosity lubricant which could result in a higher film thickness, for example in piston ringlliner lubrication.
Turning to automotive lubricants, Dr. DATE (Japan) stated that from the point of view of energy consumption and of anti-pollution, friction modified SAE ‘7.5 W-30’ low ash, low phosphorus oil has become a major product on the market in Japan whilst in Europe and USA SAE 1OW-30 grades prevail as the low fuel consumption engine oil. He asked about the possibility of low viscosity oils going down to ‘7.5 W’ or 5 W grade in the western market, even though there may be some disadvantages such as high oil consumption and wear. Dr. DATE believed that these problems can be solved by mechanical and additive technology. The author agreed with him in principle on the latter point but felt that the apparent differences between Japan, USA and Europe regarding the SAE ‘7.5 W’ viscosity level of fuel efficient engine oils might simply be a question of nomenclature. In Europe such oils-with a low temperature viscosity midway between the upper and lower limits of the SAE 10 W gradewould be described as SAE 10 W oils since ‘7.5 W’ does not exist officially in the SAE J 300 viscosity classification. The author agreed that disadvantages regarding oil consumption and wear could be encountered by moving to the SAE 5 W level