Assessment of the Low-Temperature Incompatibility Risk of Commercial Engine Oils 941976

A portion of the Institute of Materials database which contained data on more than 650 multigrade oils was searched to obtain an estimate of the percentage of oils that meet SAE J300 low-temperature pumpability requirements but exhibit properties which make the low-temperature properties suspect. The suspect oils studied either failed the Scanning Brookfield test (SBT) or produced significantly different viscosities in the one-day mini-rotary viscometer (MRV) test and the two-day MRV test, which uses the slow-cool, TP1 cooling cycle. Several of these commercial multigrade oils were obtained from the Institute of Materials (IOM). The oils were then blended with off-the-shelf commercial (CO-numbered) oils having the same SAE W-grade designation and evaluated in the two-day MRV test (TP1-MRV), which has been a reliable predictor of engine lubricant pumpability characteristics. A number of failures were recorded and some of the off-the-shelf oils were found to be more likely to fail than others.

The low-temperature rheology of the IOM-supplied oils identified them as being suspect formulations. In this report they are referred to as rheospecific formulations. Conversely, the rheology was not suspect for the majority of CO-numbered oils that were incompatible in the TP1-MRV with the IOM-supplied oils. Such oils are identified herein as rheolatent formulations; they have good low-temperature performance in themselves, but are victimized when combined with the rheospecific blends.