In a sea of snake oil and false promises, Kano Labs products deliver. Like Aero Kroil, Kreen is a fantastic product.
My daughters 3.5L Altima had a faint lifter noise at 135K. Not anymore. It was gone within minutes by just idling in the driveway. I used the recommended dose in the fuel too. I'm not going to wax poetic here about how adding it to fuel smoothed out the idle etc., but this engine runs as new, fuel economy is back to 27 mpg highway.
Based on the results with the Nissan, my 08 4.2L F150 w/ 66K got some similar love. The idle improved, highway mileage went up almost 1 mpg.
Both vehicles were well maintained, so no horrific sludge to report but the drain wasn't exactly typical either. The Nissan was black, the Ford a funky coffee/amber with the prominent Kreen scent.
I'll be using it periodically, more so as a fuel system cleaner.