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RESULTS of an experimental study of the viscosity characteristics of motor oils at low temperatures and their influence upon cranking torque and circulation within the engine are presented by the authors. At temperatures in the neighborhood of 0 deg. fahr., even oils of asphaltic origin appear to possess some plastic characteristics, while those of the mixed and paraffin-base types deviate widely from the generally accepted laws of viscous flow. Oils of these latter classes have apparent viscosities which tend to increase with decreasing shearing-stress and to become somewhat greater than might be expected from a study of their characteristics at normal temperatures. However, as resistance to cranking the engine is due mainly to oil in thin films on the cylinder walls, the relatively small temperature-viscosity coefficient of the wax-bearing oils gives them a marked advantage over those of asphaltic origin, an advantage which becomes greater as the temperature is lowered.

THE PAPER suggests a criterion for the tendency toward overheating of plain journal bearings of the high-speed type. The application of a criterion consisting of the product of oil viscosity by the square of the running speed is considered on a heat-balance basis and is compared with a series of observations of crankcase temperatures in a number of typical cars. Quoting the fact that in a plain journal bearing the coefficient of friction is a function of the term “viscosity times rate of sheer divided by unit load,” the author states the symbols and units employed and analyzes heat generation in the fluid film. An analysis of the dissipation of frictional heat is presented also, together with a discussion of the subject of bearing-temperature estimation. Curves are presented which resulted from data based on observations taken during a series of tests on a number of representative passenger-cars on the Indianapolis Speedway.

ONE method employed in a fundamental investigation of the composition of lubricating oils as it affects the viscosity characteristics has involved the synthesis of viscous oils by polymerizing a wide range of olefins with a condensing agent, such as aluminum chloride. Many thousand gallons of synthetic lubricating oils have been made within the last two or three years from olefins produced by cracking paraffin waxes. Details of the process have been published previously and hence are not included. The present paper deals with the characteristics of two such oils that have been synthesized in commercial quantities. The raw materials and the process of manufacture make these more expensive than ordinary motor oils, but their temperature-viscosity characteristics make them desirable for use in transmission and steering mechanisms and in hydraulic shock-absorbers, as they are less susceptible than the usual oil to viscosity changes with changes of temperature.

THE Conradson carbon-residue test is the generally accepted method for predicting the relative quantities of carbon an oil will deposit in an engine. This belief arises from the fact that, although publication of results of earlier researches in this field have shown that volatility of the oil is a controlling factor, it has been assumed that in all cases volatility is measured by the carbon-residue test. The results of tests conducted by the authors, covering a period of about two years, show that no such general relationship exists when the carbon-forming characteristics of a wide variety of oils are considered. This conclusion is drawn from 50-hr. tests of a large number of commercial lubricating oils in an engine operating under fairly heavy load and at moderate speed. The authors found that the volatility of the oil is the primary factor in engine carbon-deposition, and a laboratory method was developed for indicating the total volatility of a motor oil.

THIS paper represents an attempt to appraise the general automotive-fuel situation from the viewpoint of its relation to farm-tractor fuels. In particular, the probable effects of demands for fuels other than gasoline upon costs of production and distribution have been tied-in with engine operation and maintenance costs for the purpose of indicating the most logical course for fuel and engine development. In general, the farm-tractor fuel-problem is a very important one from the viewpoint of the tractor user, due to the fact that, as farm tractors are generally used, fuel is a major cost-item amounting to more than one-third of the total cost of operation of the tractor. In spite of the fact that many other considerations logically outweigh fuel costs in importance-particularly availability of the equipment and its capacity during the seasons of peak demand-this item continues to be one which is scutinized most carefully by the user and emphasized in tractor sales.

RECENT active interest in the use of commercial butane gas as a fuel for highway-transportation equipment, particularly on the Pacific Coast, indicated to Mr. Barnard the advisability of resurveying the field of possible substitutes for gasoline, especially as regards butane. Since rapid developments in the conversion of truck fleets to use butane as fuel took place in the West, Mr. Barnard considers the possibility of the general use of butane in this class of service. After going into detail regarding the chemical properties and performances of butane and gasoline, as well as their economic aspects, Mr. Barnard concludes that an attempt to supply butane under the conditions necessary for highway units eventually would result in a final cost to the operator-on a gallonage basis-higher than that prevailing for regular gasoline. He states that no very widespread use of butane as a fuel could occur without increasing the demand to a status at which the cost would be prohibitive.

SINCE it appeared reasonably certain that the key to the presence of sludge deposits, regardless of form, lies in the oxidation of the oil to give the small amounts of asphaltic substances which are inevitably present, the authors prepared the following paper to summarize and appraise the evidence on this point and to present a method for measuring oil stability. After discussing sludge, its composition and effects, engine observations of oil oxidation are stated and the conclusions are reached: (a) that appreciable oxidation of each of the oils occurred in a 50-hr. run; that (b), variation in engine output markedly influenced oxidation of the oils while variation in sump temperatures did not; and (c), that even with the wide difference in the character of the oils used, chloroform insoluble material (“carbon”) did not vary greatly but appeared to be determined mainly by engine condition. A comparison of laboratory and engine tests is made and the Indiana Oxidation Test is described.

IT is recognized that volumetric efficiency-and therefore specific output - can be increased by reduction in manifold temperature, pressure drops, and the like. The present investigation has been directed at the determination of the changes in volumetric efficiency which may be obtained by fuel-volatility variations. The results of this work may be summarized briefly as follows: (1) Very substantial improvement in engine performance can be obtained by taking advantage of suitable volatility increases. (2) A given degree of improvement in the distribution characteristics of a fuel can be attained by combining “front-end” and “total” volatilities in a fairly varied manner. (3) The distribution characteristics of a gasoline can be judged satisfactorily by using the amount evaporated at 158 deg. fahr.

THIS paper represents an attempt to illustrate the values of octane-number improvements in aviation gasolines in terms of increased earning power of current-type transport airplanes when proper provisions have been made in the original designs. The procedure consists in computing the change in earning power of a gallon of gasoline when octane-number changes are reflected in altered fuel consumptions or take-off load capacities.

Annually, the Coordinating Research Council (CRC) sponsors a nationwide survey of octane number requirements for current model passenger cars. In this review, based on surveys from 1965 through 1974, trends in octane number requirements reflect changes in engine design and exhaust systems to meet the legislated limits on emissions. The average requirement dropped approximately 5.5 Research octane numbers over the ten-year period with the most dramatic drop of approximately 3.0 octane numbers in 1971 when car manufacturers recommended use of 91 octane gasoline. The trends toward lower average requirements since 1971 have been determined with both leaded and unleaded fuels. Incidence of surface ignition knock and rumble was about one per cent in 1965 and tended to disappear after 1971. The average spread of octane number requirements between 10 and 90 per cent of cars satisfied increased about 2.5 numbers over the period.