No engine can diesel without a fuel source... If it is dieseling, it is
getting fuel... If it is getting fuel then the mixture rod is not
cutting the fuel flow off completely... If the mixture is not cutting
off properly then your carb needs a rebuild... Res ipsa loquitor...
As far as the heat range, go with the recommended plug in whatever
brand you like... If the current plugs are hotter than recommended
either he was having lead fouling problems, or oil fouling problems...
Or he got a heck of a deal on the plugs...

denny - who's engines do not diesel on mogas...