Cars! Acceleration vs MPG

I don’t own a car. I haven’t owned my own car for about 6 years, though a shared one for the first 4 of those. I’ve lived happily car-free for the last few years. This lifestyle isn’t possible for everyone, so most of us buy a car. But how do we chose? And why do car commercials get to arrogantly advertise their pick up has the best MPG in class of 27 MPG? 27 is a really crappy number. My first car, a 98 Chevy Cavalier got 32 MPG and I was a wild teenager driving that thing. Why have we progressed so little in the past 15 years? Why does a Google search find fuel efficient to mean 30+ MPG and not 50+ MPG?

I sat down to do some research about the historic relationship of acceleration vs MPG in America. We have, as a country, systematically chosen power over efficiency. A blogger, Dan, at put together a wonderful article that I will pull from for this post. He speaks to a big political document called the Light-Duty Automotive Technology, Carbon Dioxide Emissions, and Fuel Economy Trends: 1975 – 2013 (which reads a lot like I imagine the IPCC report reads to non-climate folks…). It’s long and a little tedious to the uninitiated. So, just like I do with the IPCC, I’ll highlight the most insightful graph:

Figure 2.3 from the EPA annual report.

The fuel economy, or MPG, of cars has basically flat-lined since 1980. Without changing much about the vehicles weight, car manufacturers have dramatically increased performance. This graph gives well researched evidence that car manufacturers have no real drive to improve our efficiency. Okay, so why does this happen?

Now here is something really cool that Dan did: he made a lovely correlation plot of efficiency and power. He found that for every percentage drop of fuel economy you give up, you get 3 percentage points of power. This means that it always feels like a better deal to give up a little efficiency to gain a lot of power. Ugh.

Beautiful plot!

What does that power really get you? Wouldn’t you rather save the money at the pump? I don’t expect to change anyone’s mind with this. But it’s worth thinking about. Luckily Obama has some legislation in place that will help efficiency get to were it ought to be. But for now I’m happy to live car free and hopefully by the time I want a car I will have more options for “high efficiency” vehicles.  …and then I found this:

I can’t even tell you how many versions of this meme I found! I have no words…


About Samantha from SocialMath

Applied Mathematician and writer of
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1 Response to Cars! Acceleration vs MPG

  1. How flattering that you reproduced my graph…thanks for the plug. And congrats on your PhD!

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