All mineral derived base stocks used in lubricants contain waxy hydrocarbons that come out of solution when temperature decreases. They can form a three-dimensional wax crystal network that can totally immobilise the oil. In formulated engine oils some additives have a “waxy” or crystalline structure and further contribute to the formation of a crystal network that impairs oil flow. Waxiness is evidenced at low temperature by higher pour-point, yield stress and viscosity compared to a wax free oil. Inadequate oil flow to critical parts of the equipment may result in costly failures. The function of Pour-Point Depressant (PPD) is given in the name. They depress pour-point by inhibiting the waxy structures that form in mineral oil at low temperature. But for modern engine oils pour-point has little relevance and isn’t included in modern international engine oil standards. Industry experience over the decades has replaced pour-point by other more valid assessments of an engine oil’s suitability at low temperature. In particular low temperature pumpability by Mini Rotary Viscometer (MRV) due to its inclusion in SAE J300 specification is the primary test. In some cases this is now required on used oil, and most recently in Europe on oil oxidised in the presence of biodiesel by CEC-L-105-12. However PPDs exist or have been developed which are effective in these evolved low temperature requirements of engine oils.In this paper we show that PPDs are available which are effective against this latest European CEC L-105 requirement, although extra consideration must be given to their selection. We also show that multiple low temperature requirements tend to narrow the choice of acceptable PPDs, and the choice of PPD can be strongly influenced by the presence of other additives in addition to the mineral oil. These combined with the extra requirement for CEC L-105 has made PPD selection more difficult, but based on our work reported here this new challenge can be met by correct PPD selection.
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