We use Mobil DTE-26 hydraulic fluid in our Hydraulic presses. Just got back an oil analysis which shows Tan numbers. What is an acceptable number. The highest reading was 3.4 for one press. The Lab doesn't know what is acceptable or not. I called mobil tech services and the guy I spoke to couldn't understand why we were doing TAN on hydraulic oil. The manufacturer recomends TAN testing annually. Any comments on what is an acceptable number. Thanks, Chris Ward, Entegris Inc.