Comparative Performance of 12 Crankcase Oil Mist Separators

Closed crankcase ventilation (CCV) systems are required in most automotive markets in order to meet emissions regulations. Such systems usually require a separator to recover oil and return it to the sump. Many end users fit improved separators in order to reduce intake/aftercooler contamination with soot/oil. This study measured clean and wet pressure drop and filter capture efficiency in 12 different crankcase oil mist separators which are commonly used for either original equipment (OE) or aftermarket fitment to passenger vehicles and four-wheel drives (≤200 kW). The filters tested spanned three different size/rating classes as well as included both branded and unbranded (imitation) models. In addition to filters, separators (often termed “catch cans”) and an OE cyclone separator were also examined. Testing was performed under controlled laboratory conditions using methods equivalent to previous work and current mist filter test standards. All separators were tested at flow rates between 50 and 250 lpm in both dry and “wet” (saturated with oil) states. Filtration/separation efficiency was also measured. Separators were compared based on quality factor (ratio of capture efficiency to pressure drop). A wide range of quality factors were found; however, in general, the filters were found to be superior to the catch cans, while the cyclone had the lowest quality factor. The branded filters were found to be superior in terms of quality factor, mainly due to the fact that they contained a greater quantity and/or finer separation media compared to imitation models.