Can anyone help with my question. I have 8400 miles but I'm researching how to change the trans fluid. I've looked at videos on youtube but can't find one for optima/2016. I know how to take the bottom shield off and should be able to locate the drain plug. It seems there is a plastic overflow cap/opening on the side of the trans. The fill port from videos is on top. you have to take off all the air handlers and expose the top of the trans. Is the fill plug a 22mm or 24mm size plug? small plug? I've seen some fill through the overflow plug and not even filling up top. I'd like to just drain (about 4.5 qts I've been told) and then just fill through the top fill plug and avoid the side plastic plug. I have not taken the shield off yet to see the trans nor the air handlers to find the fill plug. I recently couldn't get the oil filter off and had to take it to kia to get them to remove and put my fram filter on. Any comments or help would be appreciated. I plan to do it next spring at 12K miles or so.