Thursday, February 3, 2011

ice + ICE = Math class

Wednesday ended up being another moist, icy, wintry day that necessitated almost constant defroster use, and I knew the ICE (internal combustion engine) would stay on in my first trip of the day, bringing down the mileage. I also have a couple unavoidable short trips for clients, knocking down the mid-50s mpg for a one-way of my main trip to 44.8 mpg or 5.25 L/100km after 15.9 miles/25.6 km.

I knew on the way home, being a night drive on pure ice again, that it would be great to try some hypermiling with few cars on the road.

After I got home, with the return trip tacked on I was back up to 51.6 mpg/4.56 L/100km. This seems disappointing (only 44.8 up to 51.6?!?), but, of course, the drive straight home without detours to clients is shorter at 12.4 miles/20.0 km, and you can't average mpg just like that.

Which brings us to today's math lesson :-)

Here's a convenient formula for calculating mpg for the last segment of driving you've done, like for calculating the way home of a roundtrip drive. Most people need a ScanGauge, but if your car has instaneous mpg like the Prius, try it out. Of course, you can figure it out on your own, but sometimes it's more fun to be lazy and just use whatever you find on the internet!

It supposes a certain amount of information, like that you wrote down the distance traveled and displayed mpg after the first part of your trip. These are represented by distance1 (in miles) and mpg1 in the formula.

You also need total distance traveled in miles and total trip mpg, respresented by distancetotal and mpgtotal in the formula.

Just calculate the second segment of distance, represented by distance2, by subtracting your first leg from the total distance.

Plug it all in...

And I got 64 mpg or 3.68 L/100km on the way home yesterday in freezing temps!

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