Technical Paper
Pour Point Depressant Robustness after Severe Use in Passenger Car Engines in the Field and in the Sequence IIIGA Engine
2005-05-11
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.