On a TV show called Myth Busters, they tried the most common methods of killing an engine. Sugar, Drain cleaner, mothballs, potato in the exaust ect... Most did little to affect the engine. Some even made it run better. The only one that worked was puting some bleach in the tank. No explosions, but the engine died abruptly and all the metal parts oxidized and rusted with in hours.

Ya know, just an fyi sorta thing, man.