Over the years, my hard used kettle's lid vent got gunked up with grease and wouldn't turn unless it was hot. The grill likewise had hard gunked on grease near the ends of the bars that wouldn't come off no matter what I did. Two nights ago, I used the Kettle Pizza I bought three years ago for the first time and buried the thermometer well past 700 Fahrenheit. It couldn't have been that far off a thousand degrees Fahrenheit. The pizzas cooked in under two minutes each and they were great, but on cleaning up the grill the day after, I discovered that all the gunked up crap was gone from the grill and the stuff jamming the lid vent had gone too so it spins freely cold again for the first time in years. I guess it doubled as an oven self clean cycle for the kettle, which also makes me glad I let it burn down for quite a while before cooking the pizzas. They probably wouldn't have turned out well at all if I whipped them through while the crap was still burning off.
Still, good to know for future reference that this is one way of getting rid of the really stubborn grease...