MPG Efficiency Score

NOTE: I duplicated this from the Prius Main Forum since it wasn't getting any traction over there. I probably should have posted it here in the first place

I have been thinking about this for a while. How can we compare various trips with an MPG Efficiency Score? Bear with me here!

I wanted to compare the variables of a trip and combine them into one score. The variables I came up with is miles, MPG (real) and Avg MPH. I needed a way to weight each one of these variables so that when they are all combined a single score is tallied for comparison to other trips.

Miles should directly affect the score, but if the other variables are the same, and you go twice as many miles, should your score double? I don't think so, but the farther you go at a given MPG and Avg MPH should increase the score.

Obviously, MPG should be the highest weighted variable since this is what we are trying to increase. But, if you go 2 miles at Avg MPH of 20 mph and get 70 MPGs, how would that compare to a trip of 30 miles averaging 40 mph and getting 55 MPGs?

The last variable of MPH needs to be fairly heavily weighted so as not to overly reward a high score for going too slow. When people post their trip info, very few put in the Avg MPH.

So, I came up with what I thought would be the perfect hybrid vehicle stats and this would be a score of 100. Everyone would love to see 1,000 miles out of a tankful of gas. If a rough tank size was 10 gallons, of usable fuel range, then you would have to get 100 MPGs to achieve the 1,000 miles per tank. Also, most people would love to go 75 MPH and achieve the last two variables.

I'm sure this would be up for debate, but humor me here! So now the key is to come up with a weighting factor for each variable to achieve a perfect score of 100.

Here is what I came up with:

Var. Factor Score
Miles x .06 1,000 x .06 = 60
MPG x .25 100 x .25 = 25
MPH x .20 75 x .20 = 15
-----
100

I have attached a spreadsheet file in which you can plug in various trips and compare them to one another. You can compare tankfuls or shorter individual trips to each other.

As an example here are some results:

Miles MPG Avg MPH Score
34.7 62.7 41 26.0
35.0 63.3 38 25.5

608 53.8 39 57.7
521 56.9 30 51.5

With the spreadsheet it's easy to see how each variable affects the overall score.

I know this was a long post and I hope everyone understands my concept. Please feel free to comment and suggest changes!