ok, here's my rant:
Gallons Per 100 Miles = GPCM
I’m pretty sure I didn’t come up with this structure, I probably read it online somewhere and grabbed onto it with the full grasp of my mind, claiming it as my own for years afterwards. GPCM or Gallons Per 100 Miles (C being the roman numeral for 100) is a far superior standard compared with MPG or Miles Per Gallon. Condensing the arguments about Logarithmic reperesentation vs. Geometric represenation, GPCM offers easily comparable metrics of the efficiency of vehicles, whereas MPG can be deceitful (especially at the low end).
You have a fleet of vehicles, half of which get 10 MPG and half of which get 40 MPG. Both are driven in such a way that they each used 50% of the fuel budget for last year. You have the choice of increasing the efficiency of either half of your fleet by 10 MPG for the next year. Both increases are exactly 10 MPG. Assuming next year is going to include the same mileage per vehicle, which is a better investment?
Choose now, like now, now. Write it down or something. To kill space, here’s a poem by Billy Collins:
LINK FOR THOSE WHO DON'T WANT TO READ:
http://www.youtube.com/watch?v=56Iq3PbSWZY*You are the bread and the knife,
*the crystal goblet and the wine.
*You are the dew on the morning grass
*and the burning wheel of the sun.
*You are the white apron of the baker
*and the marsh birds suddenly in flight.
*However, you are not the wind in the orchard,
*the plums on the counter,
*or the house of cards.
*And you are certainly not the pine-scented air.
*There is just no way you are the pine-scented air.
*It is possible that you are the fish under the bridge,
*maybe even the pigeon on the general's head,
*but you are not even close
*to being the field of cornflowers at dusk.
*And a quick look in the mirror will show
*that you are neither the boots in the corner
*nor the boat asleep in its boathouse.
*It might interest you to know,
*speaking of the plentiful imagery of the world,
*that I am the sound of rain on the roof.
*I also happen to be the shooting star,
*the evening paper blowing down an alley,
*and the basket of chestnuts on the kitchen table.
*I am also the moon in the trees
*and the blind woman's tea cup.
*But don't worry, I am not the bread and the knife.
*You are still the bread and the knife.
*You will always be the bread and the knife,
*not to mention the crystal goblet and—somehow—the wine.
If you chose the 40 MPG vehicles, that’s a 25% increase to 50 MPG. For every 5 miles, that last 1 mile was free, or, one out of every 5 miles was free. Congratulations, you just saved 12.5% of the fuel budget for your company for the next year. Keep reading.
If you chose the 10 MPG vehicles, you doubled your MPG for a 100% increase in efficiency. For every 5 miles, the next 5 miles were free. This is a huge difference, literally doubling the number of miles each gallon of gas is able to fuel half your fleet. You just saved 50% of the fuel budget for your company for the next year. Go figure out how to increase the average MPG of vehicles that get 9 MPG to 18 MPG. Good luck.
Since we, as Americans, drive an average of nearly 70 miles daily, 100 miles is about 1.5 times our daily mileage, or really, a day of heavy driving. The idea of 100 miles, while not immediately comprehensible, is easily understood as a unit, especially when considering a full tank of gasoline (sometimes 300 miles).
Lets consider more fully the idea of presenting efficiency as GPCM instead of MPG or even GPM.
One could easily toss out the idea of GPMM (Gallons Per Million Miles), GPmM (Gallons per 1000 Miles), and even GPM (gallons per mile) by considering scale. As mentioned previously, 100 Miles is a decent measure of day to day travel. While not precise, it could easliy be “My commuteâ€, plus a trip to “the storeâ€, plus a trip to “Mom’sâ€. Easy, right? The places to which you travel most frequently probably add up to about 68 miles per day. Which means you fuel your car about twice weekly (less frequently if you have multiple cars).
The other big reason for tossing out the metrics above is ALSO scale. Gallons per million miles would give 0.0002 GPMM for a car more efficient than the 2010 Toyota Prius. That’s not easily comparable with 0.00001 GPMM for the Hummer H2. The scales other than GPCM are similarly impaired with decimals.
However, for the current generation Prius, at 40 MPG, and the current H2 at 10 MPG, the efficiencies of 2.5 GPCM and 10 GPCM are pretty easily shown. It’s easy for people to see that it costs (at $3/Gal) only $12 for 100 miles in a Prius and $30 for 100 miles in an H2. Thustly, it’s easier to estimate annual fuel cost and total vehicle use cost with GPCM when compared with MPG.
