Yes, caustic. On the top (non painted hard plastic), I let it dwell about 10 min. Cleaned the top, then applied caustic to the sides & front, let that dwell about 2 min, then sprayed it.
I was thinking maybe a truck wash detergent might be good for the painted surfaces. They're metal & painted just like a truck, so maybe no worries about paint melting. Not sure how well it would cut restaurant grease.
Yeah, it does look like a trash can. It is for grease only, like the lid says. Most of the grease carts at my accounts are all metal, but a few have these types.