Browse Publications Technical Papers 2005-01-2174

Pour Point Depressant Robustness after Severe Use in Passenger Car Engines in the Field and in the Sequence IIIGA Engine 2005-01-2174

The new ILSAC GF-4 specification for Passenger Car Motor Oils includes a measurement of low-temperature viscosity after the Sequence IIIGA engine test.
The measurement is conducted according to ASTM D 4684, the well known TP-1 MRV (Mini Rotary Viscometer) procedure. While the limits are the usual values found in SAE J300 which are no measurable yield stress and 60,000 mPa.s maximum, it is tested five degrees Centigrade warmer than called for by the fresh oils' SAE W grade. The need for this new measurement and specification is based on the finding that some PCMO lubricants' low-temperature/low-shear rate viscosities, but not necessarily their higher temperature rheological properties, were seriously degraded in severe oxidative environments.
Because of this new focus on low-temperature rheology after facing a severe oxidative engine test, it became of interest to understand the robustness of the Pour Point Depressant which is the additive usually responsible for controlling wax related cold temperature rheology properties.
SAE 5W-30 oils, otherwise fully additized, were formulated with and without Pour Point Depressant (PPD) so that fresh oil, used oil, and used oil with PPD added after use could be compared relative to cold temperature TP-1 MRV behavior. These oils were degraded by 1) laboratory mechanical shearing, 2) field service in extended drain taxi tests, and 3) Sequence IIIGA engine tests.


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