I did not get an accurate reading before HHO but was around 20mpg.
Built a $40 tero cell out of wallplates does 1/2 -1 lpm depending on amp draw. I run around 3/4 lpm
Running one extender on the O2 sensor. Got a light and just let it burn

Anyway got a consistent 25mpg after about 1 week or running.
PROBLEM is my CRV idled WAAAAY down. We are talking 150-300rpm idle. It would die sometimes at red lites. But otherwise ran great. Ran it for a month getting 25 mpg. But when it started the low idle I cut unit off. After about 80 miles idle went back to normal. And down to 22mpg. The way I have figured the mileage is different gas stations different driving conditions etc. And average 25 over a month.
Any ideas WHY the low idle. I quit trying to cut off the CEL and just lrt it burn.