Mine is Rain-X. Before a road trip I do all the normal things, top off oil, check tire pressure including the spare, hide a few tools in the tire well for emergencies etc. But the most important thing I do is clean all of the glass, and Rain-X ALL of the exterior windows, even the mirrors.
It seems like no matter where we go, if it’s a long drive we will hit at least one heavy downpour, or one grey day of drizzle. Rain-X all around is a godsend. I even rain-X the mirrors, taillight and headlight covers.
What do you do before a road trip, Oppo?
(editing to add - that’s what I did last night, Rain-X all over the place and cleaning all the glass in the car)