Comments on: Myth: Fuel efficiency at the low end of the scale — MPG vs GPM (OR news from geek dad) http://blog.sciencegeekgirl.com/2008/08/06/myth-doubling-your-mileage-will-cut-your-driving-costs-in-half-or-news-from-geek-dad/ explorations and inspirations... in how we learn science Mon, 06 Feb 2012 23:52:22 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Getting Called Out « Damn Lefties http://blog.sciencegeekgirl.com/2008/08/06/myth-doubling-your-mileage-will-cut-your-driving-costs-in-half-or-news-from-geek-dad/comment-page-1/#comment-1416 Getting Called Out « Damn Lefties Fri, 22 May 2009 15:42:10 +0000 http://sciencegeekgirl.com/?p=347#comment-1416 [...] a more detailed rundown, you should check out Science Geek Girl.  You can also see my comments there.  But the nub of the argument is contained in this graph I [...] [...] a more detailed rundown, you should check out Science Geek Girl.  You can also see my comments there.  But the nub of the argument is contained in this graph I [...]

]]> By: sciencegeekgirl http://blog.sciencegeekgirl.com/2008/08/06/myth-doubling-your-mileage-will-cut-your-driving-costs-in-half-or-news-from-geek-dad/comment-page-1/#comment-330 sciencegeekgirl Mon, 08 Sep 2008 18:25:39 +0000 http://sciencegeekgirl.com/?p=347#comment-330 Hmm, my optimal speed appears to be 105 mph. But that's only because I value my time so highly. If my time is cheap, then I do find a local minimum at 78 mph. One thing I notice is that if the gas prices double (to $6 per gallon) then it starts to be much more economical to drive slower, because the price of gas becomes more expensive than the price of our time. I heard recently that, considering how many man-hours are saved through running machinery on petroleum products (rather than using our muscle power), either gasoline should be many hundreds of dollars per gallon, or conversely, our time should be valued at pennies per hour. So, when you plug in very high values into this calculator, you start to see more realistic money/time/gas equivalencies. Very nice calculator, Rhett! Hmm, my optimal speed appears to be 105 mph. But that’s only because I value my time so highly. If my time is cheap, then I do find a local minimum at 78 mph. One thing I notice is that if the gas prices double (to $6 per gallon) then it starts to be much more economical to drive slower, because the price of gas becomes more expensive than the price of our time. I heard recently that, considering how many man-hours are saved through running machinery on petroleum products (rather than using our muscle power), either gasoline should be many hundreds of dollars per gallon, or conversely, our time should be valued at pennies per hour. So, when you plug in very high values into this calculator, you start to see more realistic money/time/gas equivalencies. Very nice calculator, Rhett!

]]> By: Rhett http://blog.sciencegeekgirl.com/2008/08/06/myth-doubling-your-mileage-will-cut-your-driving-costs-in-half-or-news-from-geek-dad/comment-page-1/#comment-329 Rhett Mon, 08 Sep 2008 02:38:42 +0000 http://sciencegeekgirl.com/?p=347#comment-329 First, great site. Lots of good stuff here. Second, related to this issue, I created a "optimal commuting speed calculator" that determines how fast you should drive. If you drive too fast, your efficiency goes down. If you go too slow, you lose money that you could be making from working. So, how fast should you go? http://www.dotphys.net/page1/page10/efficiency/calculator.html First, great site. Lots of good stuff here. Second, related to this issue, I created a “optimal commuting speed calculator” that determines how fast you should drive. If you drive too fast, your efficiency goes down. If you go too slow, you lose money that you could be making from working. So, how fast should you go?
http://www.dotphys.net/page1/page10/efficiency/calculator.html

]]> By: sciencegeekgirl http://blog.sciencegeekgirl.com/2008/08/06/myth-doubling-your-mileage-will-cut-your-driving-costs-in-half-or-news-from-geek-dad/comment-page-1/#comment-328 sciencegeekgirl Mon, 18 Aug 2008 02:39:19 +0000 http://sciencegeekgirl.com/?p=347#comment-328 Ooh, Tom, that's a great example. My *own* difficulty with thinking about mpg versus gpm really highlights how tough it is for us to think about things that don't behave linearly. I mean, I'm good at math, I can do calculus, got an A in statistics, but this problem keeps twisting my head around. Thanks for the illuminating comment! Ooh, Tom, that’s a great example. My *own* difficulty with thinking about mpg versus gpm really highlights how tough it is for us to think about things that don’t behave linearly. I mean, I’m good at math, I can do calculus, got an A in statistics, but this problem keeps twisting my head around. Thanks for the illuminating comment!

]]> By: Tom http://blog.sciencegeekgirl.com/2008/08/06/myth-doubling-your-mileage-will-cut-your-driving-costs-in-half-or-news-from-geek-dad/comment-page-1/#comment-327 Tom Sun, 17 Aug 2008 22:15:49 +0000 http://sciencegeekgirl.com/?p=347#comment-327 This reminds me of a trick question from radioactive decay and half-lives, which I will adapt — you have a car that gets 10 mpg and trade it in for one that gets 20 mpg. (any doubling will do) This saves you X amount of gas for your favorite trip. If you wanted to upgrade to an even better car, what mileage improvement do you need to again save X amount of gasoline? You need infinite mileage; as Dave pointed out, you've already saved 50% of the gas, so to save that amount again, you have to use no gas whatsoever. This reminds me of a trick question from radioactive decay and half-lives, which I will adapt — you have a car that gets 10 mpg and trade it in for one that gets 20 mpg. (any doubling will do) This saves you X amount of gas for your favorite trip.

If you wanted to upgrade to an even better car, what mileage improvement do you need to again save X amount of gasoline?

You need infinite mileage; as Dave pointed out, you’ve already saved 50% of the gas, so to save that amount again, you have to use no gas whatsoever.

]]>