- you don't have to set a tent and fix on the ground;
- the car seals better against dust;
- high fees to bring heavy tent back in an airplane;
- the car has A/C for desperate times.
Greatest thing about sleeping in the car: you just arrive at your spot and that's it! Nothing to set. You can go exploring or take a well deserved nap after the 16 hours from Reno to my spot.
I'm tall and before Burning Man I tested a few cars and realized I do not fit common cars neither common SUVs. So I went with a Mini Van, that can fold and stow all back seats down and have a long floor. The minivan had enough space to put a bike inside, so I didn't had to buy a bike rack.
Also, before Burning Man I tested sleeping on the floor with only two duvets as bed. My back hurt, so i bought the cheapest inflatable mattress and it worked like a charm. Filled with my lungs only. It was $15 on wallmart. Goodwill had one but I was afraid of leaks, so I chose to buy a new one.
Prepared mini vans for camping, such as those from Jucy Rentals or Escape Campervans make a way better use of the available space inside and have better things such as a kitchen - but they are expensive. My minivan was a regular one and I just spread everything on the floor and had to sleep alongside with cans of food, water jugs, clothes and leds stuff. It was a mess.
I strongly recommend that you buy several boxes and organize things, one box for canned food, another box for cutterly, another for party things, another for personal cleaning items. Boxes can be piled up making better use of vertical space. Even cardboard boxes would have helped me. I had only one spoon, one fork and one knife. Sometimes I couldn't find my fork neither my spoon, so I had to eat with a knife.
Put all your water jugs on the same place so you can figure your consumption during the week. I had my jugs on several places and at the middle of the week I was afraid I would have not enough water and started saving. On the end I still had 3 full jugs lost somewhere on the car.
About fuel: I filled the tank in Reno than filled it again in Gerlarch. I wasted two hours in Gerlarch, but that gave me peace of mind. With a full tank on Burning Man I was able to run the A/C a few times with no worries. After Burning Man you can reach Gerlarch with a little less than half of your tank, even if you get into stuck into the pulsing thing. If you want to fully use A/C everyday, than bring a 10 gallon gas can with you, it's half of a full tank.
Buy a cheap small table so you can heat your food outside the car and not set everything into fire. I found one for $6 at wallmart.
Buy a cheap camping chair, because you do not want to seat all the time inside the car. I found one for $7 at wallmart.
Get a bucket ($5 at home depot) that will collect gray water from dish washing, put clorox every now and them to prevent stinking. Leave it outside the car. Before departing, use a funnel and put that gray water inside used jug of water. Put some tape over the lid so it does not spread gray water on the floor on the trip back.
About heat: I used no shade structure, but I did two things:
a) taped outside my car several reflective foams - That helped reducing heat, but after mid-day, there's nothing that can help and my body refuses to sleep with all that heat. A/C is the only thing that helps, if you have fuel.
b) I parked close to a camping trailer, so after 4PM it produced shade and I could sleep a little before the night events.
One big mistake was to use duct tape to fix the reflective foam outside the car. After BM, it was impossible to remove the glue. I found a place and paid US$ 25 extra so the guy could clean it good. He had a special glue removal product (probably kerosene) and did a great job. Full car cleaning was $75 + the $25 + I changed the air filter. It was a super clean car after that.
About showering: To clean myself without shower I used "Epic Body Wipes" and it felt very fresh. For the special parts I used soap, a bottle of water and a towel.
About cooling stuff: No cooler. Didn't bother buying ice. Yeap, nothing like a can of hot beer to feel stronger for the day. No refrigerated food. Only a mix of dried campign food and canned food. Coffee, trail mix bars, cocconut juice, odd yellow juice... everything hot. Yeap. I missed a cooler. I do recommend getting at least a plastic tray so you can buy ice and have a cool beer.
About heating food: I only used one gas can, but please, bring at least two. If you're going to cook for real, not only heating like me, bring 3 cans of butane/propane gas.
For key safety: I bought a key box with code so I didn't had to worry about carrying the key around playa. It was a large one because car keys can be bulky. I left it attached to the door. WordLock KS-052-BK. No problem with dust.
Mini vans usually have an AC 115v port, but the car engine must be on, so I choose to carry a portable power bank battery to refuel my cameras.
For bike safety: My bike lock was this one on the link below and it was enough to lock wheels on itself, no keys to carry, just don't forget the code. Steadfast U bike lock B01M0AQ9JB model SF708. No problem with dust.
For peeing: a juice jar with a safe lid. Every morning, I took this human orange juice to the porta-potty. It does stink a little and clorox may help, but pee+bleach does produce weird fumes. Empty the damn thing every morning, for sanity.
Go to Goodwill before Wallmart. You'll find duvets, knifes, pillows, towels, boxes and many other useful things. Wallmart, however can have a few cheaper things than Goodwill, like the camping table.
I only did this because I was alone. I experienced a lot of freedom and gained many extra hours for not wasting time buying ice or setting camp. No need to make things nice, just trow yourself on the air mattress when you're tired. No clue of what time it was.
However, if you feel like destroying your marriage, go to burning man with your spouse, a single car and no mattress. Buy only one fork. Bring two gallons of water. Arrive with an empty tank. Suggest a 10-some in Orgy Dome.