Ronald K. Jensen

Fuel Efficient Engine Oils, Additive Interactions, Boundary Friction, and Wear

Abstract In order to encourage and accelerate development of advanced engine oils which would further contribute to improvement of engine fuel efficiency, Ford developed and made available to the oil industry a new engine test for determination of fuel efficiency of engine oils. This test, called Sequence VIB, was incorporated into the ILS AC GF-3 engine oil standard to be introduced around the year 2000. The main features of this test are increased emphasis on benefits derived under boundary/mixed lubrication conditions and improved retention of fuel efficiency during engine oil use. Friction reducing capabilities under boundary lubrication conditions can be improved through application of effective friction reducing additives, such as molybdenum dialkyldithio-carbamates (MoDTC), which, in combination with zinc dialkyldithiophosphates (ZnDTP) and other antioxidants, must provide good retention of friction reducing capabilities and also adequate antiwear properties. Formulation of such additive systems requires better understanding of various factors affecting performance of MoDTC and their interactions with other additives. From the results of our studies it is clear that ligand exchange reactions between MoDTC and ZnDTP and oxidation and antioxidant reactions involving base oil components, additives, and intermediates derived from them are all important in optimizing the performance and maximizing the benefits derived from these systems. These reactions, although occurring first in the bulk lubricant, also play a very important role in tribochemical conversions in boundary contacts where they are enhanced by more severe conditions. Thus, fundamental understanding of mechanisms and kinetics of these reactions is essential in the process of designing optimized lubrication systems that provide efficient and lasting friction reduction. Along these lines, this paper is intended to review available information, present the most recent data, explain some of the observations, draw some general conclusions, and outline future needs.

Oxidation and antiwear retention capability of low-phosphorus engine oils

Future vehicle emission regulations both in the US and Europe will require maintaining catalyst efficiency for longer mileage intervals. In order to achieve this requirement, chemical restrictions are being placed on elements in engine oil that can poison catalysts. Most of phosphorus and a significant amount of sulfur in current engine oils come from zinc dialkyldithiophosphates, ZDDPs, which are a class of cost-effective multifunctional additives providing wear, oxidation and corrosion protection. Reducing ZDDP concentrations raises oxidation and wear concerns. The overall purpose of this research is to look at the antioxidation and antiwear capability of low phosphorus engine oils containing 0.05 wt% phosphorus and the potential of engine oils formulated without phosphorus. In addition to fresh oils, used oils drained from fleet vehicles were also analyzed and evaluated. The results indicate that by appropriately selecting and balancing supplemental phosphorus-free antioxidation and antiwear additives the antioxidation capability can be improved for low phosphorus and even non-phosphorus oils, and the antiwear performance of low phosphorus oils could be maintained or even improved.

Gas-Liquid Chromatography of Oxygenated Compounds Related to the Autoxidation of n-Hexadecane

Abstract Gas chromatography has been utilized for analysis of a series of compounds related to n-hexadecane autoxidation. Several stationary phases have been tested and Silar-10C has been chosen for the separation of the C16 oxidation products. The selection was based on the thermal stability of the stationary phase and the resolution among the C16 compounds. Relative retention data obtained for selected oxygenated compounds and some of their trimethylsilyl derivatives are reported. Gas chromatographic analysis of reaction products from the autoxidation of n-hexadecane is then discussed.