system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does an oven auto-clean with no problem and leave behind white ashes, but a dirty grill that is overheated can cause a scary-ass fire?

Isn't the principle the same? Heat to a high temp and turn the grease to ash? An oven can be cleaned easy-peasy one afternoon but the porch will be damn near burned down that evening.
gpt
Your oven should have significantly less grease in it than a grill.  If you're getting that much grease into your oven, you're doing something horribly wrong.  Your oven should have, at worst, some bits of food or cheese or a *little* bit of grease that will burn out quickly.  But grilling usually involves dripping fat and grease all over the place.

Also, your oven is somewhat closed, so there's less oxygen to feed the flames.  But mostly there should be less grease and fat.