I bought a bottle of the AMSoil product and had a real hard time getting it into my fuel tank. It appeared to have a neck too short to open the inner flap in the filler tube. I was filling up. A couple of minutes after I left the gas pump I got a check engine light. I had the codes read and it is the oxygen sensor. Question - is there an older product not compatible with modern engine parts that has the same visual appearance of the label that might have been old stock on the shelf? I have exchanged a couple of emails with AMSoil tech support but just getting a dance asking for more information. Was there such a product that could damage the oxygen sensor? After a while the check engine light went out. It was out when the codes were read and it has not come back on. Is this an explainable behavior? I really do not want to replace the sensor if it is not needed.