the Sanctimobile vs. global warming

On the way back from Kirkland to Seattle last night, my Sanctimobile passed 100,000 miles. I tweeted this, and before long somebody in Zuckerberg's data mine asked just how much carbon dioxide I'd not emitted over the years. What follows is, I hope, a more precise accurate calculation than I did elsewhere.

The Sanctimobile helpfully tells me that it gets 43 MPG. This is about 20 MPG more than the average car, and certainly over 20 MPG more than the average car ten years ago. So how much gasoline haven't I burned?

100K miles / 20 MPG = 5000 gallons ≈ 19,000 liters

The specific gravity of gasoline averages 0.74 depending on the grade, so:

19,000 liters * 0.74 kg / l ≈ 14,000 kg

Converting that to raw carbon is where things get a little hazy. [ETA: No pun intended.] Gasoline is a mixture of many different kinds of hydrocarbons, with octane being about the mean by molecular weight. C₈H₁₈ has a molecular weight of 114 and change of which 96 is carbon, so that's 84% carbon in gasoline:

14,000 kg gasoline * 84% ≈ 11,800 kg carbon

Since the molecular weight of CO₂ is 44 of which 12 is carbon:

11,800 kg carbon * 44 AMU CO₂ / 12 AMU carbon ≈ 43,300 kg CO₂, or 43 tonnes (metric tons). That works out to nearly 49 short (i.e., reg'lar USA) tons of CO₂ not emitted by Imminent Ex, the Wendling, and me over the last ten years.

Not too shabby. I seem to recall gfish calling Priuses "faggotty" when I first got mine. Not that he was jealous or anything. I wonder if he'd say the same today.