This all probably sounds nuts, but here are my oil systems:

I wash out and recycle glass jars, but peanut butter jars are difficult to clean and will end up getting fat into the water system. So I keep the peanut butter jars for oil.

I also keep a bendy, steel decorating pallet in the kitchen for scraping out fat from the grill tray and rack. You’re left with some fat that you can wipe off with kitchen paper, which you can also use to wipe the pallet knife. Then washing up liquid and a splash of boiling water from the kettle.

There can be quite a lot of oil in leftover food, like sauces, too. I use a silicone spatula to scoop it off before washing.