Saturday, May 21, 2016

Miles Per Dollar

I tweeted this a few days ago:
"Gas for motorcycle: 2.855 gal, 245.9/gal, $7.02, 230.4 miles."

I later tweeted:
"Crunching the numbers, that's 80.7 mpg on the motorcycle, or 32.8 miles per dollar. How many mp$ does your car get?"

We don't think about miles per dollar much, though I'm sure any car owner can proudly recite their vehicle's miles per gallon statistic. But that contains a level of indirection that makes the number less comprehensible. Who cares about mpg? Nor does it matter that prior to May 16, my last motorcycle fill-up was April 23.

What really matters is how much it actually costs to drive the car. You don't spend gallons, you spend dollars. Even saying it only cost me 60¢ to drive downtown and back, as I tweeted back in April, is lost on most people, as they have no basis for comparison. Let's instead make that figure more explicit: Miles per dollar.

As a real-life figure, let me go back to February 28, the last day I myself filled the car's tank.
"Gas for the car: 10.53 gal, 189.9, 87 octane, $20.00, did not fill but came close."

I did not tweet the miles traveled on that tankful, but do have the information, as I know we get 20 miles per gallon with that car. So, do the math. 10.53 gallons times 20 mpg equals 210.6 miles, divided by 20 dollars, conveniently becomes 10.53 miles per dollar.

That then becomes a number you can wrap your mind around. Every 10 or so miles I drive the car costs me a dollar, at least in the figures from February 28.

Of course, every situation is different. Every car is different, and the price of gas changes daily. Today, for example, gas is 249.9¢/gallon. Same car, same amount of gas purchased, but this time that purchase is $26.31. Do the numbers this time, 210.6 miles divided by $26.31, we get 7.98 miles per dollar. Now, every eight miles costs me a dollar. A four-mile drive to the store costs a buck in gasoline.

Think about this in terms of a daily commute. If I drove to work, 12 miles each way, hardly unusual for anyone in my neighborhood who works in the city, that's a 24-mile round trip, or $4 in fuel. $20 a week. About $90/month, ad infinitum, if you did nothing differently. It's also pretty close the the current cost of a monthly zone 1 bus pass.

Think also what a return to the $4 gas we were paying just a couple short years ago. 10.53 gallons would cost about $42; 210 miles of that works out to five miles per dollar.

All of this becomes irrelevant when you stop driving voluntarily. Figure out how to get around without consuming gasoline.

1 comment:

  1. Who cares about miles per gallon? How many miles per dollar does your car get?