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Our basic understanding of the chemical and physical nature of soot, its interaction with lubricant components and its role in promoting wear and oil thickening in heavy duty diesel engines continues to grow. Our current study in the GM 6.5L engine focuses on examining the effects of variations in base stock type (Group I vs. Group II), viscosity index improver or viscosity modifier (VM) chemistry (OCP vs. dispersant OCP), zinc dithiophosphate (ZDP) type and dispersant type (low MW vs. high MW) on roller follower wear, viscosity growth and other measured responses. In this study, more robust fluids were tested producing very low wear results and minimal viscosity increase of the lubricant. Fluids containing dispersant OCP (DOCP) and high MW dispersant produced a lower degree of wear, whereas varying the ZDP type (1° vs. 2°) showed no effect on wear. The use of Group II base stocks was associated with significantly lower viscosity increases.

Interactions between automatic transmission fluid (ATF) components and composite friction materials and their effect on friction system performance continues to be an active area of interest to the automotive industry. A more fundamental understanding is needed of how base fluids, ATF additives, friction materials, and transmission design interact to produce the observed transmission system performance and durability. We herein report results from investigations carried out using a relatively thermo-oxidatively stable polyalphaolefin (PAO) base fluid treated with components representative of several additive types we previously reported to have significant negative effects on frictional performance. Secondly, we investigated a conventionally refined 150 N base oil treated with a calcium sulfonate detergent previously shown to improve friction performance.

The lubricant is a key component in the successful operation of a manual transmission, but it is important that the interactive effects with the friction material are understood. This paper examines the effect of several key additive components on the friction and wear performance of a single sinter composition in a carefully controlled laboratory test. In addition, the test method allows one to develop information about the shift behavior of the fluid-synchronizer material combination which provides useful information about shift quality. From the original experimental design program a predictive model was developed and an optimized formulation was tested as a validation of the results.

The use of a copper diesel fuel additive in an emission control system improves particulate oxidation. This expands the operability of available systems by reducing the particulate mass loading and related external energy consumption required during regeneration. Easier, more frequent regenerations improve overall engine/system efficiency and reduce thermal stress on filtration media. Procedures for optimizing additive use are presented. In addition, the results from a health study are reviewed.

Interactions between a Zinc dialkyldithiophosphate (ZDP) and three different commercially available succinimide dispersants were observed through changes in solutions behavior, as determined by viscometry and Fourier Transform Infrared spectroscopy (FTIR), and four-ball tests. The viscometric response observed for two component blends of ZDP and succinimide dispersant in white oil changed as a function of the molar Zn to N ratio, indicative of specific interactions. The break in the viscometric response curve occurred at Zn:N=0.13 for all three succinimide dispersants. FTIR spectra of the same ZDP-dispersant blends were examined and similar Zn:N dependencies were observed. Four-ball tests measuring wear scar diameter, seizure load and weld load showed a dependence on the Zn to N ratio similar to that observed by viscometry. At very low Zn to N ratios wear and seizure load were decreased, while at higher ratios the seizure and weld loads were increased over that for ZDP alone.

Piston ring land deposit formation is a key performance criterion in the ASTM Sequence IIIE engine test. Because engine testing of lubricant formulation variables is expensive, a ring land deposit bench test was developed replicating the Sequence IIIE bulk oxidation and deposit formation mechanisms. Following an initial bulk oxidation of the candidate oils, deposits similar in chemical composition and morphology to Sequence IIIE ring land deposits are produced in a modified panel coker apparatus. Good correlation with the ASTM Sequence IIIE engine test has been established. Lubricant additive and base oil effects on oxidation control and deposit formation have been investigated. Their influences on lubricant formulation strategy are discussed.

Accurate, timely field test results are necessary to develop and validate lubricants meeting frequently changing performance requirements. Field tests can also provide valuable information about performance deficiencies (e.g., soot related wear) which are not apparent in laboratory development tests. Since field tests are time intensive and increasingly expensive, it is imperative that the data generated provide meaningful results with reasonable expenditures. The data generation and analysis process are being constantly improved according to the principles of quality management. Part of the process improvement focuses on accurate, realistic treatment of the data since more variation is typically observed in field tests than in laboratory tests. One of the most difficult analytical processes occurs with oil consumption data.

The International Lubricant Standardization and Approval Committee (ILSAC) GF-2 requirements for Passenger Car Motor Oils (PCMOs) will lower phosphorus limits from a maximum of 0.12% allowed by ILSAC GF-1 to a maximum of 0.10%. In effect, the ILSAC GF-2 phosphorus limit removes 17% of the most commonly used antiwear and antioxidant additive in current PCMOs, zinc dialkyldithiophosphate (ZDP). This paper outlines some work in ASTM Sequence V engine dynamometer tests to quantify the effect of reducing the ZDP on valve train wear and sludge formation. Engine data for the Sequence VE, the proposed Sequence VF, and the modified Sequence VE are presented. These three tests summarize the evolution of the Sequence V from the Sequence VE for GF-1 to the dual plug Sequence VE configuration for the GF-2 specification.

Intentionally adding water to oil, in the laboratory, provides an indication of the oil's ability to tolerate the presence of water. Various characteristics, such as emulsion, haze or separation, may be observed. Some blends of oil and water have been shown to form structures when left undisturbed. A visual, qualitative, storage test is capable of detecting this phenomenon as the presence or absence of structure. However, the time frame of formation can be on the order of days or weeks and is sensitive to handling and temperature effects. Quantitative methods are required for any evaluation of chemistry, temperature and handling effects on the rate and strength of structure formation. This paper describes rheological and electrical methods which directly and indirectly measure the tendency to form a structure at the molecular level, yielding rate of formation and strength information.

Multifunctional additives can compensate for lower quality diesel fuel. Performance and quality have been decreasing worldwide. This has resulted largely from increased use of heavier crude oils and more severe processing to achieve necessary fuel product mix. Fuel additives provide the refiner and marketer with an economic approach to restoring performance and quality. Additives can be formulated to solve many problems related to deposits and wear, which are major factors affecting engine power, economy, emissions and durability. They are of critical importance to the vehicle owner/ operator to maintain dependability and low operating cost. At the same time, the refiner benefits economically through the use of lower cost crudes, greater operational flexibility and ease of adjusting final fuel blends to meet specifications. Typical additive components include: detergent dispersants, inhibitors, stabilizers, cetane improvers, and flow improvers.