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Technical Paper

The Impact of Evolving Automatic Transmission Fluid Specifications on Base Oil Selection

Automatic transmission fluid (ATF) performance is determined by the choice of lubricant basestocks and additives used to formulate the fluid. The lubricant basestocks employed set the fundamental low temperature capabilities and resistance to oxidation of the fluid. Over the last decade, ATF specifications issued by the major North American transmission builders have required significant improvements in low temperature fluidity and oxidation stability. These required improvements have begun to limit the number of basestocks capable of producing suitable fluids. The practical impact of this evolution is that API Group I basestocks are rapidly becoming incapable of producing the new generation of ATFs. Recently issued, and proposed, specifications will clearly continue this trend. Future ATF formulations may well be forced to move to API Group II, Group III and/or synthetic base fluids to meet these increasing performance requirements.
Technical Paper

In-Service Low Temperature Pumpability: Field Performance vs. Bench Tests

The most important property of the engine oil is its ability to reach all engine parts. Once there, it can build an oil film which protects these parts from wear and ultimately from destruction. No other lubricant property is relevant if the oil cannot be delivered to the critical engine parts. Thus engine oil pumpability, especially pumpability at low temperatures when the viscosity of the lubricant is the highest, is crucially important. The crankcase lubricant industry has recognized this, in requiring good low temperature pumpability for the last three decades. While good low temperature properties of the fresh oils are a necessary requirement for a lubricant, they are not sufficient to ensure the lifetime performance of the oil in the engine. The oil gradually ages in the engine and its properties, including low temperature pumpability, change.
Technical Paper

Acid Neutralization and Engine Hardware Corrosion Protection through Heavy-Duty Diesel Lubricant Additive Chemistry

One of the primary functions of modern heavy duty diesel (HDD) lubricants is to protect the engine against corrosion, which is typically accomplished by additives providing alkaline material, commonly represented as total base number (TBN). The majority of the TBN in HDD lubricants comes from ash-containing over-based detergents, with various metallic base and soap chemistries. In this publication, we discuss several overbased detergents and their efficacy in acid neutralization, as well as the resulting impact on corrosion protection. The performance differences are compared in a number of stationary API CJ-4 and CK-4 HDD engine screener tests. Furthermore, these results are confirmed with field trial data, including a comparison of CJ-4 oils with the upcoming API FA-4/CK-4 oils. The selection of overbased detergent type provides varying levels of acid neutralization and corrosion protection.
Technical Paper

Studies on the Interchangeability of Group III Base Oils in ATF

We have compared five different, commercially produced, API Group III base oils in a next-generation, OEM automatic transmission fluid (ATF) formulation. One objective of this work is to understand the impact of base oil selection on the performance properties of finished ATF. This may help us to develop technically sound criteria for allowing interchange among premium Group III base oils in both factory-fill and service-fill ATFs. The performance data, measured from lab bench tests, include such properties as seal swell, low temperature viscometrics, oxidation life, and LVFA static and dynamic friction. Certain properties of the base oils, such as low temperature viscosity and oxidation stability, have a strong impact on the ATF performance. However, there are many chemical similarities between the Group III base oils, and this results in little to no differences observed in many performance areas.