A new test has been developed to predict the quantity of air entrained in a crankcase oil under automobile engine operating conditions. The test involves measuring the temperature and API Gravity of the oil before agitating with a rotary mixer and again ten minutes after mixing has ceased. From this API Gravity measurement, it can be determined whether the oil will cause air entrainment related problems. This test appears to be more sensitive and more severe than the ASTM D-892-74 test toward air entrainment. The test can be made in one hour or less and the apparatus is very inexpensive.