In June 2005, I bought a car. It's a 2004 Toyota Corolla. In a fit of nerdiness, I decided to track my gas usage in this new car. A year and a half later, I've got some good, basic data. Perhaps I'll be able to give better stats after this semester of studying advanced statistics, but I've got some simple stuff right now.
In this year and a half, I have:
- driven ~16,650 miles
- used ~517 gallons of gas
- spent ~ $1350 on gas (!!)
Some caveats: I did loan my car out a few times. Once or twice, someone else obviously put more gas in without writing anything down (this was a happy little surprise, as I didn't know people had given me more gas. yay!). Therefore, the numbers are approximate, and the gas mileage for two tanks was skewed upward. Still, remember that we're working with approximates. Additionally, I spent a good chunk of miles here driving across the country (~3000). During almost all those miles, I pulled a trailer, and that made my gas mileage dip.
Turns out that my average gas mileage is ~ 32 mpg. On longer trips with no trailer, I can get that number closer to 40 by watching my RPM. My in-town mileage seems to be about 19-30 mpg, depending on how far I go in town (in Gold Beach, my in-town mileage was horrible because my car never had the chance to warm up. I'm glad I minimized my trips there by only driving to and from work).
I also figured that I spend about 8 cents a mile on gasoline. Not too shabby, since I got reimbursed at the rate of 40 cents a gallon when I got paid by work (of course, that's also supposed to include insurance and maintenance).
I wish I'd kept better track of what kind of driving I was doing on each tank. I started out doing that, but I gave it up after it got hard to remember (especially in Seattle, where I did a mix of driving types) when I was only filling up once or twice a month).
It seems, according to my chart, that my gas mileage varies widely. I wonder how much of that is statistical artifact versus actual truth. Also, it appears that filling up my tank more often gives me lower mileage numbers -- the majority of my poor mpg tanks appear to be ones where I filled up when my tank was only 1/4 down. Overall, I find the range of numbers strange, and I'm not sure why stop and go driving (which occurred fairly often in Seattle, especially when driving to Mariners games) didn't hurt my tank anywhere near as much as in-town driving in Gold Beach appeared to.
I will continue to take more data, and I think I'll add a new column for type of driving. I'm interested to watch those numbers and see how they continue to change over time.