Hey Craig,

What is your commute like? How's the weather, the traffic, and are there any long stretches of road with no services? And what exactly are you preparing for? Normal day to day events, or a full emergency?

I was in your exact situation, 100 mile round trip commute each day in a Forester. I didn't have to carry anything too extensive becaust the weather in SoCal is generally mild, and forturnately my commute was through the most populated area of the country (not so fortunate because of traffic). There would be thousands of people passing 24 hours a day, every day, so no need for survival shelters or hunting traps and stuff like that. At worst, you'd walk less than a mile to the nearest pay phone or store and hang out for a while. I also didn't want to carry a whole lot, because the vehicle isn't that large, and I didn't want to take up valuable space. I would carry some of this stuff at a minimum.

1) AAA card. I actually didn't get a membership until recently, but I've been in a few cars where AAA has come to the rescue.
2) Cellphone. I personally don't own one, but I would recommend an emergency phone or something

It may not seem very "survival" oriented, no cool knives and firestarters and stuff like that, but I'm betting those two things will cover you in 99% of the situations you will ever face on a daily city commute. If you drive through a metropolitan area like i did, chances of not being able to get services are very, very small. In addition to that, I would carry things just to use for everyday emergencies

3) Portable Jumpstarter - because you don't always want to wait for AAA to come along, could take up to an hour.
4) Extra clothes
5) Couple bottles of water
6) Snacks
7) Headlamp (for changing a spare tire)
8) Change your spare to a full-size spare, get rid of the doughnut
9) Extra money for emergency gas or stuff
10) First Aid kit
11) Road flare or reflectors (very important if you commute at night)
12) A couple of tools (Screwdrivers, wrench, pliers, etc)
13) Fire Extinguisher
14) Wet Wipes
15) Maybe a sleeping bag if you need it

You might have to add more stuff depending on you situation, and most of the stuff you probably already carry in your bag. I've had friends who had longer commutes on the east coast, even when they were stranded by a snowtorm and couldn't make it home, the only tool they ever used was a credit card. Rent a cheap motel room, have a nice dinner, and watch TV until it passes.

Since you have a new car, I wouldn't worry too much about major breakdowns, so no need to carry a bunch of spare parts and a full toolset. As the vehicle gets older, I do carry a little more, but not much more, unless I'm planning on going somewhere more remote. And I wouldn't recommend carrying gas cans inside the car for obvious reasons.