From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Recommended practice and reasons for crankcase oil changes in passenger cars for winter and summer conditions.
| Identifier | ExFiles\Box 145\2\ scan0147 | |
| Date | 22th January 1937 | |
| Recommended Practice For Crankcase-Oil Change in Passenger Motor Cars* Winter The severity and duration of cold weather, the number of engine starts in a given period, and the amount of idling largely govern the rapidity with which crankcase oil becomes contaminated in winter. For cars operating at temperatures below freezing, oil should be drained at least every 500 miles. Where atmospheric temperatures consistently below 10 deg. F.{Mr Friese} are encountered, and cars are operated on short runs with many stops and starts or with prolonged idling, draining should be on a time rather than a mileage basis. Under such conditions, oil should be changed at least every two weeks. When temperatures below zero are consistently encountered, crankcase temperatures may be abnormally low. Under such extreme conditions, the oil may become dangerously contaminated and require draining after a few days' use. Summer The frequency of summer draining depends largely upon car speed, atmospheric temperature and the rapidity with which dust and other contaminants accumulate in the crankcase. In general, crankcase oil should be changed every 1,000 to 1,500 miles, the interval depending upon the severity of operating conditions. Cars driven at sustained high speeds in hot weather should be drained at least every 1,000 miles. The same recommendation applies for cars operated on dusty roads. Where dust storms are encountered, crankcase oil should be drained immediately after leaving the dust area, regardless of mileage. Air cleaners also should be cleaned thoroughly at the same time. When cars are operated regularly in dust areas, the crankcase oil pan should be dropped and cleaned frequently. Under the most favorable conditions, a car may be driven safely as much as 1,500 miles before draining. However, it should be realized that abrasive dust is always present, and that gradual contamination of crankcase oil is always taking place. While cars are occasionally driven further without apparent damage, the saving in oil cost per year is too small to be considered in comparison with the possible sacrifice in engine protection and efficiency. REASONS FOR CRANKCASE-OIL CHANGES The essential reasons for changing crankcase oil may be stated as follows: 1. Water contamination: It is a fact, not commonly known, that more than a gallon of water is produced in an engine by the burning of one gallon of gasoline. This water is ordinarily in the form of vapor or steam; but, when the jacket-water temperatures are low, some of this water condenses and gets into the crankcase. This condition is accentuated by low air temperatures, and becomes extremely rapid in sub-zero weather. It is particularly acute when short runs and frequent starts are necessary, as is the case with cars used by physicians, inspectors, and salesmen. The same applies to motorists who use their cars only for going to and from work. Under these conditions, while the jacket-water temperature may reach a normal range, the crankcase remains cold, and water in it is not driven off by evaporation. For winter operation, this accumulation of water is the major factor in oil deterioration, because, almost invariably, it mixes with the oil to form a thick, mayonnaise-like emulsion. Leakage of anti-freeze solution from the cooling system into the engine greatly accentuates the formation of emulsions. These often interfere with normal lubrication, leading to disastrous results. During the cold period of every winter, a large number of cases are encountered in which bearings, pistons, and cylinder walls are ruined because the lubricating systems become clogged by emulsions. Serious damage also has occurred from water freezing in crankcases when cars are left standing exposed to low temperatures. * NOTE: The American Petroleum Institute has approved the Recommended Practice for Crankcase-Oil Change in Passenger Motor Cars prepared and submitted by a group of oil men who constituted themselves a Committee on Oil-Change Practice. This report was considered and approved by a large number of oil companies, and then submitted to the Automotive Advisory Committee of the Institute. On the recommendation of that committee, it was approved by the Executive Committee of the Institute on January 22, 1937. | ||