I happened to have some Mean Green degreaser under my kitchen sink and tried that one evening. It worked very good. I sprayed it on and waited about 5 minutes or so and most of the crap wiped off on a paper towl or rag. A few stubborn spots got retreated and I used a stiff old toothbrush to take the rest off. I used the same brush between the fins. Its cheap from Family Dollar and maybe Dollar General has it too. I heard that Dawn Power Degreaser works great too but don't leave on too long. I think either works unless you want to invest in sonic cleaners and such. I did the antifreeze/crockpot trick and it does turn the color depending on the metallurgy. I forgot what exactly it reacts with in certain metallurgy but some engine makers or years have it and some don't. I did it with an old OS 40 once and it changed the color to dull gray. Its still ran ok, but took away the luster. Also, don't do the antifreeze thing indoors because warm antifreeze gives off toxic fumes (so I was told). It doesn't smell good anyway.