We have all seen it. My buddy is a career long haul truck driver. He is anal about maintenance on his truck and his pickup, without them he doesn't eat. The lawnmower is a whole 'nuther story. He called today, it wouldn't start and he was ready to drop a match in the gas tank. I scurried out there before the whole subdivision became an inferno.
I checked the air filter, it is likely the original 2008. Filthy and wet with water (left outside and neighbor turned the sprinkler on). The zone control cable is stretched, the switch is not breaking contact when the bail is pulled back. I asked him if he did any more than add gas and pull the rope. He thinks he changed the oil a couple of times.
I'm going to do a complete service for the cost of parts, he has done me more favors than I care to count. No point trying to edurmacate him, you ever try to push a rope? Sigh.