Compact Car Camping

My family of 4 have been able to camp for 3 nights at a time out of a compact car.  I know we could do many more, perhaps weeks or a whole month.
Why?
Consider these big advantages:
High miles per gallon. 30, 40 or more in a compact car. You can go a long way for modest gas costs, travel faster than in a motor home or towing a trailer.
Saving on hotel bills. campgrounds cost 20 dollars a night more or less depending on whether you have electricity.
Clean accommodations:  hotel rooms are notoriously dirty with studies finding bacteria on light switches door knobs, remote controls  and stains on bedding and carpeting (which can be seen under 'bluelight').
Flexibility: Campgrounds: may be found almost everywhere, often in places where there are no motels or hotels and surprisingly, often reasonably close to urban destinations such as Washington D.C.
Most are clean safe and cheap often with running water, flush toilets, and showers
Look online to find them: Look for public and private campgrounds.  In Michigan there are more than 1000 locations.
Interest: Many, many campgrounds are near, even adjacent to great sites: natural wonders, waterfalls, beaches, historic places, even free concert venues such as Interlochen in Michigan.

How?
Compact light, cheap durable gear is now available:  tents, tarps, mattresses, sleeping bags, chairs, lanterns, cooking gear all have evolved to be highly practical for compact car camping.
Rooftop carrier or rear cargo carrier might be added to your car but these can affect mileage by increasing wind resistance so I prefer to pack everything inside and keep all items compact.
I am investigating mounting some gear outside the car in ways that do not increase wind resistance but have not yet come to any recommendations on this. 
One idea: I like the 'diamond hitch' as a possible way to lash some items to the roof or trunk lid, or behind the trunk (like a bike rack - but how do you keep the license plate exposed to view?  Perhaps move the license plate.)
Gear list:
Tents: one large tent, or two smaller tents that are easier to set up and take down.
ground cloth: blue poly tarp costing a few dollars.
tarp for dining fly: 10 x 10 feet or more blue ploy tarp with rope and poles - or tie it to trees - look for campsites where they are available.
sleeping pads and or air mattresses: rugged comfortable expensive ones are available or the cheap vinyl ones work.
sleeping bags: in warm weather sleeping bag liners alone - compact and cheap to buy could be used.
personal gear: clothes, towel, dental care, grooming items, etc. - keep in duffel bags and or day packs easy to stuff into any corner of the trunk or cab.or between the legs of passengers.
clothes: To keep down clothes volume, carry only 2 or 3 changes and do laundry in the middle of the trip. Take clothes that have multiple use. For example, pants with zip off legs can serve as shorts or long pants, and may even serve as swim suit.  A flannel shirt can serve as a towel.  On cool (but not cold) nights, sleeping in a hoodie (along with a blanket or sleeping bag liner) can make a carrying a bulky sleeping bag unnecessary.  The 'camping gear' of the ancient Scots was a wool cloak serving as coat, rain cover, and sleeping wrap all in one.  A cloak might be a good idea today.
chairs: 3 leg folding 'butt rest' chairs. , or carry no chairs - picnic tables available at most campsites provide seating, or sit in the car with the door open if you want a comfortable seat. The bottom of the rear seat comes out easily in the Ford Focus and in many other cars and could be used as a seat pad in a camp.
table: small folding - could be homemade of plywood - or carry none, and use the picnic table.
cooking gear, eating equipment: carry in small 'soft' containers, not one large hardwall ones one so they can be easily be stored away in odd corners of the trunk, or  under seats, or in a glove box.
Carry an electric hot plate to cook on when electricity is available, and a wide cooking pan. Or gas stove and canister. Hot plate and pan (I like stainless steel ) can do a lot: heat water, cook vegetables, grill pancakes or hamburgers, in fact do everything a grill can do. Another option - carry an electric grille, but don't carry grille if  you have hot plate and pan.  Hot plate and pan are more versatile than a grille.
Food:
On some trips, to save space we do not carry food except snacks.  After setting up camp - and the car is empty - we go to a food store.  (many campgrounds are a short drive from food stores). Also, on some trips we carry breakfast food only and drive to fast food for lunch and dinner - Often we do this while on a day tour of the area.  Another option: prepare a picnic lunch to eat on the trail or during the road trip. This can be cheaper than fast food.
In general all 4 of us can be full with fast food for under $10: with one caveat, don't order their drinks.  Water costs nothing, cleans the teeth (pop eats them away with acid), helps digestion, and has no sugar that can make children go 'hyper' and contribute to weight gain. Water is truly the drink of the Gods.
examples of cheap fast food: 2 subway footlongs divided in half, a Little Ceasers pizza  (with bread sticks), 'value meal' items at most fast food chains.
If you carry all of your food, consider carrying it in small packets rather than one large box or bin so it can be stuffed away in any oddly shaped corner of the car.  Some food items can even be carries on a rear dash.
Carry no cooler, buy only food that does not require refrigeration. a huge number of food choice exist that do not require refrigeration. See the book Voyaging on a Small Income by Annie Hill for how she does it while living on a sailboat without refrigeration.
Or, for occasional refrigerated items: get a small 'soft wall' cooler you can fold flat when not in use.  Buy after you get there, and consume quickly items requiring refrigeration or freezing such as milk, cheese, meat, ice cream, etc.

Packing it all in:
Backpackers may carry 50 pounds or more of food and gear in an area of perhaps 2 or 3 cubic feet.
A compact car can carry many times the volume and weight of gear folks carry on backpacking trips Thinking in terms of backpacking methods and gear is a good start towards successful car camping.
And, a step further is ultralight camping, in which gear and supplies are minimized in volume and weight so a backpacker might carry only 20 pounds or less in perhaps 2 cubic feet. In some cases most gear needed for camping could be carried on the floor between the feet of a car passenger. (but not the driver of course).

In the cab: going from front to back
In the glove box: car manual, repair records, title, registration, directions, pencils, paper.
In the door pockets: maps, jackknife, spoon and fork, napkins, spare key, compass, tire pressure gauge,
Between the front seats in trays and cupholders: spare change,  water bottles, pens, paper, cell phone.
plastic spoons and forks, small snacks, vaseline, sun block.
Under the seats: tools , maps, 1st aid kit,
between the rear seats including the hump between the floor pans: sleeping bags, snacks, trash bag
On laps of passengers: stuffed animals, pillows
Between legs: day packs with small miscellaneous items inside.
On the rear dash : anything flat - maps, games, magazines, floppy /broad brimmed hats (crushed flat).  Behind rear seat headrests larger objects can be placed especially on the driver side - such as cups and empty - large size water jugs (to be filled when you get to camp.  The rear dash is not a secure place for a large full water jug).

In the trunk: 13.8 cubic feet are available in a Ford Focus.
removing panels and trays over the spare tire provides more volume.  Some sources have suggested removal of the spare tire for more volume - I do not do this but it would add 3 or more cubic feet of area.
Packing the trunk:  tent to the back behind the rear seats, food and cooking/eating  items to the front heavy items low, light bulky items stuffed in above (watch out for the path of trunk 'arms' and keep that area clear.

Camping with comfort:
Camp layout:
If rain is not expected I do not put up the rain fly unless I need it for shade.
If rain is expected put the tarp up over the picnic table that commonly comes with most camping sites. Have the tent and tent doorways near the rain fly tarp to make it easy to go from tent to dining area without getting wet   And, have car parked near the dining fly on the other side from the tents.
Fire circle or cooking area on the 4th side of the rain fly, under cover if necessary.
Here is a diagram of the ideal layout:
                    tent
tent      rain fly over table       car
             cooking area
                fire circle

Gather dry firewood early and store it under cover.
Bugs: I dislike sprays.  Netted bug hats work well and are cheap.
Getting smoky and sweaty discourages bugs.  If you are camping and hiking don't be afraid to get a little smelly and dirty.   It won't hurt you.

Ultralight Camping: Easiest in warm weather.
To really go lightweight and low volume; use no tent: but use several rain flys only - with mosquito netting for sleeping.  Hammocks with netting work well for some folks especially in hot weather, though I find them uncomfortable.
Use no bulky sleeping bags, just carry sheets and one blanket per person.  (If an unexpected cool night surprises you wear extra clothes to bed).  Do not use pillows, just carry pillow cases and stuff them with spare clothes.  I forgo even the pillow case and use my duffel bag or day pack with spare clothes for a pillow.
A spare flannel shirt can serve as a towel.
I find ultralight camping an interesting challenge, a fascinating problem: how can I stay comfortable with the least lightest equipment.  And, as a further challenge, how can I get gear for the lowest cost.  Craigslist, freecycle, garage sales and flea markets help. Folks very often give up camping and find themselves with lots of barely used gear.  And, foraging for items such as tent poles and pegs, firewood, and edible plants adds more challenge.

For the ultimate challenge leave the car and all the gear and walk into the wilderness with just the clothes on your back as folks calling themselves 'primitivists' or 'aborigines' ("abos' for short) or survivalists, do  - as a recreation.   For fun they learn and practice ways to survive, even be comfortable in the wild. I can't think of a better form of recreation: exercise, healthy food, non polluting (if done right), constantly learning new things, do-able as a team or group - or alone if you prefer. baseball, football, golf, tennis, spectator sports,  running, hockey, they all pale compared to this 'sport'. The human mind and body are built to live this way, and it is the way we lived for millions of years. Study Thomas Elpel's books and CDs and you'll begin to understand.

Nevertheless,
After any hike or outing into the wild I always find coming back to my well equipped, efficient, and highly mobile vehicle a welcome moment.

Free camping: You can camp for free. National forests allow 'backcountry camping' without charge as long as you camp at a prescribed distance away from waterways, campgrounds where you have to pay, and trails. (it would be hard to enforce a ban anyway wouldn't it?). In Michigan, you can camp free in the State Forests with a 'dispersed camping permit' available from the State Department of Natural Resources.  Call them and they will send you forms for free.  Just post it at your campsite for a Ranger to see (in the unlikely event one comes by).

Now, if I just could get (build myself?) a car that I don't have to buy fuel for, a solar electric car perhaps, (and camp free in State or National forests - and perhaps forage for food in season), I might experience almost zero cost living while traveling by car, and be as free as the wind.
Imagine touring the country, touring the whole world in a compact but comfortable vehicle that costs almost nothing to operate so you don't need a bundle of money to do it - and therefore you are not tied down to a job and one place.  The world becomes yours!