Like mojavean states, the grates are coated with a porcelain enamel, almost a glass like substance. It will wear, and it might be susceptible to attack by "some" of the stronger dishwashing detergents that have potassium or sodium hydroxide in them. I quote one sentence from Wikipedia under the topic 'dishwasher'-"glass dissolves slowly in alkaline aqueous solution."... you can read the article yourself. I mentioned before, it's like the porcelain coating on French cast iron ovens, such as Le Creuset and Staub. Having said that, it would probably take years to have much of an effect. Still, I would rather have the bottom of my pans wear out this coating. The grates will take a seasoning, you just wipe them with the smallest amount of oil, and turn the burner back on. Some oils smoke less than others, refined light olive oil is good, this seasoning may burn off and stick to the bottom of your expensive copper pan, especially if it's a fresh seasoning....otherwise, not a problem, and in fact it probably protects the porcelain from wear. The big thing with cast iron, even porcelain cast iron, is to keep it dry. Sometimes you'll see a light 'bloom' of rust on it, just wipe it off. But if rust gets under the porcelain, it will lift it off and chip it. To clean, I use an almost dry scrubby sponge, and leave the bowls on the cooktop. If I spill a mess of flour, or manage to make a complete mess, I do take the bowls to the sink and rinse them there.

Do NOT put it in the self-cleaning oven. I had the same problem with my gray stove grates and thought I was such a genius using my oven to clean them. They came out beautiful the first time, and after the second time the enamel started breaking off. I finally had to get a new stovetop, this time SS with black cast iron (which has its own cleaning issues.)

How do you clean Miele cast iron grates? I found something on this site about Viking cast iron grates and it suggested using a 3m blue non-scratch pad with Easy Off. I tried this and now I have a nick on my grates. Is it safe to put them in the oven and press clean? Also, I've tried various things to get grease off the area around the burner. I now have scratches on the stainless steel. I read somewhere about MAAS metal polish. Will this work? I'm really freaking out. It is not my cooktop. Help!

I guess it would be easier if/when these babies were new, if they had been cleaned as they should have, it probably wouldn't be such a huge task. Also, given I live in SOFLA, we use the a/c 11 1/2 months a year, these are sucking air flow constantly. With so many other things to clean, I just forget about them until one day...ewwwww! I would have thought the steam cleaner would have worked, but, nay nay. I'll try Jaybirds idea and probably try pipers toothbrush idea along with it. Those of you with floor registers, you'll have to give me tips on cleaning those next - I'll be moving north and they don't seem to have the a/c vents that we have done here! Thanks all!