I work in a nuclear plant and we have EMD diesels with Mobilgard 450 NC oil for emergency back up power. The industry has had a couple of bearing failures in these diesels and the experts are searching for the root cause. The latest probable cause is foaming of the oil. My opinion is our diesels have a very large sump (350 gallons) and any foaming that takes place would dissipate before the lube oil pump would pick it up. The questions I have, if I start having ASTM D 892 foaming test performed what acceptance criteria should I apply to used oil before I recommend a change? How often should I request a foam test? Should the foam test been a test that I should have been requesting all along? And the last question, is my assumption of the large sump and the oil dissipating correct?