i do mine with antifreeze like ken said, but if you let it cook 16-24 hrs you can just take it outside and wash it off with the waterhose (and there is not enough antifreeze left on it to hurt anything).the gunk will just rinse off, no scrubbing, i do this for the purpose of looks, nothing uglier than a gunked up engine, and it does help with coooling like downunder said.