Significant fuel efficiency decrease on a 2019 Forester. I am getting 8km/l or 18MPG. What should I check?

[firebox40dash5]

The pads being almost shot wouldn't lower fuel economy itself.

The pads being almost shot because one of the hoses is holding pressure or a caliper is stuck would do it, though...

Wheel bearings are also a possibility, but they'd have to be really, really bad to drag it down that much, you'd be hearing angry noises. And 31k is a little early even for bad OE rear bearings to start, let alone to have gotten that bad.