2007 Prius using up a lot of oil

Wer you located ? This is common for a worn out 1NZ. Well worn

 

What is a "tank" of oil ?
And what "meter" are you talking about ?

Being at the low mark is a quart low.......not empty.
Given your car's age and mileage, that is to be expected.

Switching to a "high mileage" oil might help a little but probably not much.

 

Add a quart of oil when it gets to the low dot, no need to change the oil just because it is low.

If you read the dipstick when the car is cold and has sat overnight most of the oil should have drained back, so the initial reading is cleaner. I agree that if the stick is read "conventionally", which is pull it out, wipe it off, put it back, pull it out, read, there is often oil smeared up the side of the dipstick.

 

THIS.