I have been using a 1 LPM unit for a while now. To me it seems the use of HHO improves the engine perhaps by burning carbon deposits and that it runs much better even after I turn off the HHO. The key is measuring the MPG and I find the scan gauge to be a good tool to do this. I am able to reset the scan gauge and the odometer while on the highway and go 10 miles and get continuous readings of MPG and distance traveled. This has also lead me to believe that humidity is somehow involved with millage.