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. A number of bench and engine tests have been developed to predict low temperature pumpability of the aged oils, such as Sequence IIIGA, Romaszewski Oil Bench Oxidation (ROBO) and a new low temperature pumpability test under development by CEC TDG-L-105 group.
In this paper we examine the low temperature pumpability of several oils in a modern 2010 emission complaint Heavy Duty Diesel (HDD) engine. We show that good fresh oil low temperature properties such as MRV TP-1 apparent viscosity or gelation index do not guarantee good field performance. We also evaluate a number of bench tests as predictors of field ageing and low temperature performance of the used oils, and we show that while some bench tests exhibit reasonable correlation with the field, not all bench tests can predict failing performance in the field.