How level is needed for transmission fluid change?

That's close enough, you're set.

Open the fill port before opening the drain- just to make certain you can refill it.

 

Yeah just think about it. I don’t have Prius c repair manual instruction, but for various others the spec is for the fluid to be anywhere between flush with fill hole lip, to 10 mm lower.

what’s never stipulated, is that it’s maybe a good idea to have the car level. All I can think is Toyota’s repair manual writers/editors never pictured anyone other than dealership mechanics with a full lift system doing a transaxle fluid change. But common sense leads DIY’rs to: you want to do that level check with the car “roughly” level.

there’s some info in my signature on transaxle fluid change. It’s specific to 3rd Gen Prius, but still worth a read. (On a phone turn it landscape to see signatures)