"As these results indicate, fleets that have been testing our CK-4 and FA-4 formulations have consistently reported exceptional results," Smith adds. "Because we started the advanced research and testing programs for our CK-4 and FA-4 formulations in 2011, ExxonMobil is well prepared to help fleets and owner-operators have an easy transition when the PC-11 lubricant specification goes into effect on Dec. 1." CK-4 oils are a direct replacement for current CJ-4 oils and are backward compatible with today's diesel engines. ExxonMobil's CK-4 line will include synthetic Mobil Delvac 1 ESP 5W-40, Mobil Delvac Extreme – a premium synthetic blend – and Mobil Delvac 1300 Super. Available in a range of viscosity grades, Mobil Delvac CK-4 oils offer improved oxidation resistance, shear stability and aeration control compared to today's CJ-4 oils. FA-4 oils will mostly be recommended for use in model year 2017 and newer model engines.