Stability of some commercial lubricating oil addition agents in an internal combustion engine

by Charles Martin Robidart

Institution: Oregon State University
Department: Mechanical Engineering
Degree: MS
Year: 1952
Keywords: Lubrication and lubricants
Record ID: 1526328
Full text PDF: http://hdl.handle.net/1957/52683


In the mid 1930's the Diesel engine, which formerly was used only as a large, low-speed machine, was developed into a smaller high-speed engine for use in trucks, busses, and tractors. Along with these changes in mechanical design came many problems, of which a major one was lubrication. Because ordinary mineral lubricating oils quickly deteriorate, certain chemical compounds were mixed with the oils to improve their performance. Introduction of the chemical additives to the Diesel engine lubricants met with considerable success and the practice was soon followed in spark-ignition engine lubrication. The additives used now include such chemical compounds as anti-oxidants, anti-corrosive agents, extreme pressure agents, viscosity index improvers, and pour point depressants. In addition to the compounds developed by petroleum and chemical companies, other commercial addition agents, which are sold in auto supply stores and service stations, have appeared with many and varied claims. Today there are many of these "patent medicine" mixtures on the market. The purpose of this investigation was to determine the stability of a representative group of these commercial addition agents in an internal combustion engine. A small single cylinder, water-cooled Lauson was used as the test engine. It was mounted on a test stand with a direct current generator and a control panel. The procedure followed in the tests was adapted from the Coordinating Research Council Handbook. It consisted of a standardized break-in period with a reference oil, and a test time of 36-hours with an additive-reference oil mixture. The reference oil, of high rating, was procured from the Coordinating Research Council for the control in these tests. The oil or additive mixture, after the 36-hour test period, was analyzed by the following ASTM tests: Gravity, viscosity at 100 F and 210 F, flash and fire points, water and sediment, neutralization number, precipitation number, and copper strip corrosion. Photomicrographs were taken to observe the extent of corrosion on copper-lead bearing sections, cut from a bearing whose composition was 65 per cent copper and 35 per cent lead. These specimens had been present in the sump during the test run. Two different oil temperatures were utilized to obtain extremes in operating conditions. One oil temperature was 212 F and the second at 110 F, with 25 ml of water added to the crankcase. The first value simulated long, hot weather, driving conditions and the second town driving with many starts and stops and low oil temperature. The results of the tests are summarized as follows: 1. The addition of water to the crankcase accelerated the deterioration of the additive-reference oil mixture. 2. There were definite tendencies in most additives to corrode the copper-lead bearing strips. 3. The additives did not prevent carbon deposits or sludge formation to any greater degree than the reference oil. 4. All of the additives had a definite effect on the physical properties of…