When I started doing research on the O2 sensors functionality, this is what I learned. Most likely the cause of the O2 sensor and why we have this problem with them.

O2 sensor #1 by manifold reads the out put after burn. So it sees how much O2 vs unburned fuel is in the air going out. It is looking for a certain concentration. I do work with a similar device at work that trys to keep how much oxygen is put out so they don't waste it. Very expensive stuff.

Back to the point.

So number one says OK I see 300ppm.
(ppm is parts per million).

exhaust then goes thru the exhaust and some remaining fuel is burned.

O2 sensor #2 then sees 400ppm of Oxygen and says ok, we are in spec.

So, when HHO burns, we get a cleaner more complete burn. So, since we have a more complete burn, the first sensor sees 400+.

The left over burns clean in the CC and then O2 #2 sees the output which is even higher. So, it sends the ECU a voltage telling it that we are burning way to lean, due to it does not see the lower O2 out put and the ECU dumps more fuel until it sees it's 400ppm again.

Now my numbers are just for example and only that. That is how I read on several car sites, IE FORD, DODGE and CHEVY.

Pretty much, car companys as we know are in bed with the BIG OIL. More gas we waste, the more profit they make. They could come out with a better solution, IE when we lean our cars down.

But, since they don't want to come up with a super lube that keeps the frictino down and the heat. We are stuck with what we have to mess with.

I did see a lube long time ago where they ran this stuff in the oil, and with no water thru the block, kept it up near 6000 RPM for over 5 min with no temp increase. Maybe BS, due to it was one of those TV adverts.

Take my info for what its worth. That is what I read and that is our problem for the O2 sensors.