Besides these used oil samples, two different brands of clean lube oil, Pennzoil 10W-30 (labeled P-10W-30) and Valvoline 10W-30 (labeled V-10W-30) are purchased from Target store for the purpose of blank study. The reason for choosing 10W-30 grade for comparison is because it is the most popular used one, especially with Southern California’s weather condition.
The characteristics of the four original used oil samples and two unused automotive lube oil samples are listed in Table 4-2. It is obvious that there are some problems encountered with the acquired used oil samples.
First, the water content in the four used oil samples is too low when compared to reported values (possible 5%-20%, with average 7%-8% most common). In addition to conducting reactions with the original used oil samples, some samples were prepared by adding about 20% distilled water by weight (about 17% by volume, confirmed by water content measurement) ⎯ the maximum water content ever reported, and mechanically mixed by the blender. It is expected when finer and more homogeneously dispersed vesicles are formed, more interfacial contacts between the two phases will occur, which can enhance the ultrasonic irradiation reactions. The mechanical force (blender) used to make the emulsion, however, may create an emulsion state in the emulsified sample which is a lot different from its natural form.