I am thinking that the reason for my O2 constant failure and cats not working at their best could be from the oil consumption of RotellaT and T6 over time. It my not be the problem but it's just a theory. I use quite a bit of oil expesally at startup. If the chemicals that are in T and now T6 are backing on the O2 and cats, is there something that will remove it? I tried a soak in soapy water overnight but moved from the emission testing area before I could tell if there was any affect. I did notice the smell was different. It was the same smell when I put a new cat on an older vehicle. I know that's not scientific. I do know that in Europe there was reasearch on citric acid and how it could clean diesel cats. I have a gas cat but use diesel motor oil. Not sure how much of the cause of diesel cat contamination is from diesel fuel and how much, if any is from diesel motor oils.