I recently changed from a Cx-9 to Cx-90 PHEV. The PHEV because it has a battery now is taking space away from the hidden areas in the trunk storage area which I have a bunch of different items. I would have a hodge podge of things, somethings that I just moved car to car, but now I need to get smart with what I have, because my wife and switch cars often and she needs to fit a stroller I can't just have a huge bag sitting in the trunk. I have first aid kit, that I plan on keeping. I have alot of towing items, 3 hitch ball mounts (probably not needed), wiring for trailer to extend, a bag of tiedowns, plastic gloves, flashlight, towels, 2 screw drivers, various cloth bags, garbage bags, rags, flashlights, umbrella, OBD2 reader, and lot more unessary bags. It's a new car so not sure what might or might not be necessary.
One thought is to have one bag for towing in which I could pack when I tow something, yes I could forget it, but I don't think I need 3 hitch balls until I do 
Definitely do separate the towing-related stuff into a container you can easily remove. Is a flashlight still necessary these days with everyone having a phone with a decent light built in that can charge from the car? For the screwdriver, you could save a little space by switching to one multi-tip screwdriver. OBD2 readers are pretty small and should stay in the glovebox because they're delicate. In terms of tools I also pack a spanner set and an adjustable wrench. It's also worth having a can of fix-a-flat. Recently I've been thinking that carrying some spare "universal" coolant hoses (the ugly accordionized ones), one in each larger size the car uses along with some small generic line, could be worthwhile to give you a chance at roadside-fixing a blown coolant hose.
All of our family vehicles have a basic first aid kit, jumper cables, a flashlight, a few tie-downs, and at the very least a multi-tool. In the Expedition, I carry a small Packout box with basic hand tools and a small socket set, as well.
Even though my phone has a light on it, it still doesn't throw like an actual flashlight. And LED flashlights are so cheap now, you might as well. Even the little $3 ones they have by the register at Harbor Freight are surprisingly decent.
Trent
UltimaDork
11/15/24 3:17 p.m.
My answer?
Nothing.
An empty car discourages break ins. Leave a bag in view or have enough stuff in there that it looks like there might be something of value then you will have a problem.
I carry a tire gauge in every car. That's about the only constant.
Every car I own (well, aside from the caged, track-only race car) has a jacket, a hat, a pair of sunglasses, an umbrella, and some sunscreen. That's about all that I consider essential. Cars that go on longer trips get things like flashlights, gloves, towels, etc. I only carry jumper cables in the truck, though.
1988RedT2 said:
Bottle of liquor.
Good roach clip hanging from mirror.
Trent said:
Leave a bag in view or have enough stuff in there that it looks like there might be something of value then you will have a problem.
Small duffel bag with PPE gear and ratchet straps behind the drivers seat on the floor at a Holiday Inn Express.
$250 window covered by car policy - $500 deductible.
$250 of gear covered by homeowners policy - $1,000 deductible.
