Heck, that stuff is only a dollar at the Dollar General store in my area. I'd throw a buck at it to see what it does in my mower engine.
FWIW, I poured some Z-max that I swapped from OilGal into my car and I recorded the highest MPG's I've ever seen in over 9 years of operating my car. I got 54.4 mpg's on my most recent tank of diesel fuel after running two tanks of fuel in my car after I added the Z-max.
Is it simply a abberation after 9 years? I might try the Motor-Up for a buck on my other vehicle just to see what the hype is about.
Speaking of Zmax, buddy at worked bought some. He said his MPG increased as well. He was strictly basing it on the MPG counter on his pickup, so I don't know how accurate and all, but he was pretty impressed with the gain.
I remember seeing infomertials on that stuff, as well as DuraLube... The ones that they "drained" all of the oil out of the engine and ran it... Oh my...