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An investigation of an engine field-failure found low-temperature incompatibility to be the root-cause of an engine pumping failure. This was established from an examination of the rheology of the new and used oils. It was later discovered that some SAE multigrade oils that contain higher-cloud-point basestocks are incompatible with other same-W-grade oils that contain VI improvers that have a propensity to interact with wax precursors. The latter oils, which failed the Scanning Brookfield test, but not the TP1 mini-rotary viscometer test, were found to be incompatible with a number of commercial multigrade oils at low-temperature.

Results from this study indicate that the reproducibility of the CEC Standard Test Method, CEC-L-14-A-88, a diesel injector mechanical shear stability test for engine lubricants, is not applicable to certain engine lubricants. The test is subject to a material bias which is caused by operational parameters-the allowance of a broad valve opening pressure range - and the use of a relatively insensitive calibration fluid. The magnitude of the bias depends on VI improver molecular weight and molecular weight distribution, as determined by gel permeation chromatography, otherwise known as size exclusion chromatography. The bias can be minimized or eliminated, however, by determining viscosity loss at a specified gauge pressure. It was thereby possible to improve reproducibility and obtain excellent correlations between diesel injector and both gasoline and diesel laboratory engine tests results.

THE final proof of whether or not a lubricating oil is suitable for use, comes only as the result of engine tests conducted under conditions simulating those the oil must meet in service. To be of value, these tests must be carefully controlled and the results recorded in a form that is reproducible. In the case of piston-skirt deposits, it has been found extremely difficult to secure accurate quantitative results, reproducible by different observers; and to obtain a permanent record of the form, location, and intensity of the deposits. The authors' work on piston-skirt deposits has led them to develop two devices, which they have described here in detail. The first of these makes use of a reflection densitometer to obtain readings of the reflection density of a large number of points on the piston to be studied. These readings are converted to reciprocal reflectivity values, the average of these values being called the piston rating.

THE chemical problems of engine lubrication associated with wear, detergency, and oxidation stability are discussed by the authors. A detailed examination is made of the stability of lubricating oils in engines. It was found that the oil rapidly becomes contaminated with solid oil-in-soluble materials that greatly affect its stability toward oxidation: In some cases, the stability after 1000 miles of use may be 1% of that of the fresh oil. By the addition of pure compounds to the oil, and also by the separation of the components of the oil-insoluble materials, it was determined that the metal salts, particularly the halogen salts, are the effective catalytic materials. Two possible methods for combating these catalysts are mentioned by the authors. A few experiments are also reported indicating a possible usefulness of these engine catalysts in laboratory oxidation tests.

A study of the low-temperature cranking and starting characteristics of the Mazda engine is described. Measurements were made at around - 10°F, using a Mazda R-100 car in a cold room. For these experiments, the seal lubrication system-in which the oil is mixed with the fuel in the carburetor-was separated from the conventional bearing lubrication system. Cranking speed was found to vary inversely with the viscosity of the oil in the sump and to be independent of the viscosity of the seal lubricant. Compression pressure was proportional to cranking speed; oil viscosity had no direct effect on compression pressure, but was important only as it affected cranking speed. A brief investigation was also made of an apparent icing problem which hindered starting of our Mazda engine at low temperatures. The results suggest that water of combustion, produced in the first few cycles of cranking, may freeze and prevent the sealing grid from functioning properly.

The lubrication of 2-stroke cycle crankcase-charged gasoline engines by means of a lubricant admixed with the fuel is frequently referred to as “once through” lubrication. Minor revisions of the piston ring set up to make this once through lubrication concept more nearly true have improved piston cleanliness, decreased spark plug fouling, and reduced combustion chamber deposition.

This paper presents experimental measurements of oil film thickness for a statically loaded journal bearing with single-grade, polymer-free engine oils and SAE 10W40 polymer-containing engine oils under hydrodynamic lubrication conditions. Measured minimum film thickness was correlated with a bearing Sommerfeld number based on actual high shear rate viscosities with no significant difference being observed between polymer-free and polymer-containing oils. However, a significant decrease in bearing attitude angle was observed for a number of polymer-containing oils compared with polymer-free oils at the same Sommerfeld number. Using measured values for eccentricity, attitude angle and high shear rate viscosities, the total friction couple was calculated at various Sommerfeld numbers with no difference being found between polymer-containing and polymer-free oils.