I work for the water/ waste water utility in Anchorage Alaska. We have numerous stationary generators and pump engines.We used to have oil analisis done on a yearly basis but but have quit doing this as the results did not seem to be of any benefit.I geuess the main problem is we did not understand information we got back.We have a natural gas powered Waukesha with approx 50,000 hours. Management decided the cost for an oil change on this unit was exsesive at 37 gallons per change so changes would only be done when analisis showed to be necessary. Engine run conditions are ideal and long life should be expected. We are using A chevron oil for natural gas engines.As the oil approached 3000 hours, oil consumption was increasing but anailsis said oil was fine. At 4000 hours oil consumption was very hi but analisis still said oil was good. Management was considering engine for overhaul. I took this unit under my care and changed the oil. Consumption went way down and with changes done now on 1000 hour interval the engine is clean, happy and oil usage nill! I do not understand how the test could say oil was fine and yet the engine was deteriorating rapidly. I would have thought with over 4000 hours on the oil something would be turning up in the test. Am I missing something here???