Is the delta P gauge on a clay treater actually telling you anything?
Not really. This is a common misconception. The only true way to tell if the clay is working is to take a MSEP test. This test will be taken on the inlet and the outlet and compared. The reading from the outlet should be higher. A good quality fuel has a reading of 90 or better. The closer you get to 100 the better the fuel quality. If the fuel going in is 80 and the outlet is 80 or less, you would need to change out the clay.