Anytime you buy an order vehicle if the previous owner has stretched the oil changes to very high mileage between each oil change there's a possibility that the rings on the Pistons have carboned up to the extent that they don't prevent it from burning a lot of oil. So that's a big concern.
Toyota had a batch of engines called 2az-fe that were really notorious for having the Rings not seal properly and causing them to burn a lot of oil. I think what it boils down to is they designed the piston rings to not have a lot of friction by being low force between the piston ring and the cylinder wall but they went a bit too far on this one and it ended up being a very serious oil burning problem. They even had a recall on it. It really happened a lot when people didn't change the oil often. But as far as I know the Yaris does not have that engine. You can look up Toyota oil burning engines on Google or look up Toyota 2az-fe oil burning and you can find a list of the models and years that those models had that engine and avoid those. Especially when buying used because it may be outside the extended warranty repair interval. Just something to be aware of.
Toyota had a batch of engines called 2az-fe that were really notorious for having the Rings not seal properly and causing them to burn a lot of oil. I think what it boils down to is they designed the piston rings to not have a lot of friction by being low force between the piston ring and the cylinder wall but they went a bit too far on this one and it ended up being a very serious oil burning problem. They even had a recall on it. It really happened a lot when people didn't change the oil often. But as far as I know the Yaris does not have that engine. You can look up Toyota oil burning engines on Google or look up Toyota 2az-fe oil burning and you can find a list of the models and years that those models had that engine and avoid those. Especially when buying used because it may be outside the extended warranty repair interval. Just something to be aware of.