Objective: How to add windshield wiper fluid.

Which of the following solutions is more sound in terms of naive physics reasoning?

OPT: (i). Using a clean funnel pour the fluid into the windshield wiper container until it reaches the fill line. If you do not see a fill line, leave a couple of inches of space at the top of the container. Replace cap.. (ii). Using a clean funnel pour the fluid into the windshield wiper container until it reaches the fill line. If you do not see a fill line, leave a couple of inches of space at the top of the container. Do not replace cap..
(i).