I have one guy that just doesn't get it. I explain to him everyday that the 21" mower is self propelled. Everyday I see him strugging with the mowerbecause he forgets to engage the unit. I just let him struggle now. I enjoy watching him pushing it up hills. I have everything that runs 2 strokes labeled with green tags that say mix...It matches the gas can. Also the can says for trimmers and blowers only. I caught him putting straight gas in a trimmer. I saw it before he started the trimmer. And for the topper. I am mowing on one yard, he is across the street with my 62" toro. I can hear over my mower his making a horrible grinding noise. I run over and make him shut it off. Middle spindle went bad. I said "Couldn't you hear that" His reply. "Sure but it is still running it can't be that bad". Today was his last day.