A brief study in gas mileage or, How to Cut Your Gas Mileage in Half

Posted by Ryan Jerz on Saturday December 19, 2009.

The short answer: get a job that’s close to home.

I have been tracking my car’s gas mileage for almost two full years. I do it using a site called Fuelly. Fuelly has a mobile web version that is optimized for the iPhone. You bookmark it and just enter the relevant info each time you fill up. All of it gets entered and your account updates. It’s a great little tool and I treat it just like any other app on my phone.

I used to have a little graphic on the sidebar of this site showing my car’s average miles per gallon. I kept it under the heading “Moral Superiority.” Why? Easy. I got really good gas mileage. I ran anywhere from 33-36 mpg. I attributed it to the perfect storm of good car (2002 Saturn SL1, baby!) and good driving conditions. About 90% of the driving I did was on the highway during my commute to Carson City each day. There was an occasional jaunt to pick up a kid from guitar lessons or dance class, but the highway driving dominated, and thus the mileage was approaching maximum efficiency.

graph of my mileage by fuel-upAbout two months ago I got a job in town. My drive to work, while shortening from 30 miles each way to three, was now entirely on surface streets fraught with stoplights, stop signs, and slow going. To top it off, it got colder and I was moving. Moving made my garage fill up with boxes and I had to park on the street—meaning I had to warm up the car in the morning. But the real culprit here was the change in driving conditions. The graph on the left shows my mileage as calculated by Fuelly each time I fueled up. It’s an ugly trend, and one that would likely only get worse with a different car.

This was a real wake-up call regarding city versus highway driving. The Department of Energy estimates that my car would get 23 city/34 highway miles per gallon. I was generally above the highway end and am far below the city. It makes me think that the estimates on new car windows is bunk.

It also makes me think back to a Kottke post that made me really think about gas mileage. It’s a great way to think about how your car does with regard to fuel, and the only saving grace for me right now. Consider: getting around 18 mpg now while driving about 10 miles a day during the week, my car will use 144.4 gallons of gas in a year [(10*5*52)/18=144.4] If I was driving a car that was getting 15 mpg I would use 173.3 gallons in a year. That’s a whopping 20% increase in gas used, and that should really be the ultimate indicator of how you’re affecting the environment, right? For the record, I drove about 330 miles per week while commuting to Carson City [330*52/34=535.3], so I was still using tons more gas than I am now, despite my horrific miles per gallon.

Anyway, as someone who tends to be obsessive with numbers (read: baseball statistics) I found this drastic change really interesting and wanted to look into it deeper. I’ll keep monitoring my mileage and may update when I notice any other changes.

Ryan JerzRyan Jerz is an all-around good guy who wants people to eventually refer to him as "that dude who climbs mountains."

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