This past two weeks, I’ve used:

• a Prius to get groceries and dinner
• a Civic to check out an apartment in SF
• a 328i to check out an apartment in SF and visit Golden Gate Park
• a Nissan Versa to get groceries and go up to Mount Diablo to check for some of this week’s meteor shower action
• a Honda Odyssey to move from Berkeley to a new apartment in SF
• a Mini to get back over to Oakland for a Saturday homebrew BBQ

There are two ZipCar lots within two blocks from my new location in the city. The credit card style swipe is ingenious. I’ve called customer service twice and was able to talk to real human beings right away.

I can roughly quantify the opportunity to save money that I’ve created by switching from my car to ZipCar.

Assuming an average hourly cost of $10 (including SF 9.5% tax and the 10% EVP discount), I’ll save money in any month that I use ZipCar fewer than 50 hours. That seems like more than enough driving for me. The potential savings could be much higher with other people. I had access to cheap loans and cheap insurance, and I did repair work myself, so car ownership was relatively affordable for me. ZipCar is better though, because of the flexibility and simplicity I now enjoy.

The mass on either side of a chemical reaction must balance, so I thought to myself, “If a gallon of fuel weighs 6 lbs, where is the other 13 lbs coming from?”

Well, it turns out that the additional weight is from the 21 lbs of oxygen that your car sucks from the atmosphere to burn that gallon of gas! Your car also spits out one gallon (8 lbs) of water in the process. 21 lbs of oxygen fills about four phone booths (~250 cu. ft.), and 19 lbs of carbon dioxide fills about two and a half phone booths (~150 cu. ft.). If your fuel economy is 25 mpg, then the above quantities occur every 25 miles you drive.

Here’s a simple mass equation:
C8H18 + (25/2) O2 = (8) CO2 + (9) H2O
hydrocarbon + oxygen = carbon dioxide + water

Basically, each Carbon atom broken from a fuel molecule grabs two Oxygen atoms from the air, and every two Hydrogen atoms grab one Oxygen atom from the air. Breaking these bonds yields heat energy.

Is this surprising to anyone else?
Disclaimer: As this not my area of expertise, I make absolutely no guarantees regarding the accuracy of this very simple example. The real-world process of combustion involves many variables.