ExxonMobil has responded to Shell's claim that Mobil Delvac 1300 Super 15W-40 does not meet API CK-4, nor the requirements for Volvo, MACK and Cummins. In a statement issued last Tuesday, and sent to OEM/Lube News, ExxonMobil said "ExxonMobil stands by the quality of our products and re-affirms that Mobil Delvac 1300 Super 15W-40 carries valid OEM approvals and API CK-4 licensing."